Botz, you asked a lot of good questions, but I don't just want to leave you with yes or no answers, but to give a little explaination of exactly what it means and why the Church holds the doctrine that she does, so this is going to be a very long post.
Yes.
Let me first define what the Catholic Church means by the Doctrine of the Immaculate Conception. We mean that the Blessed Virgin Mary, from the first moment of her conception, by a singular grace and privilege of Almighty God, and in view of the merits of Jesus Christ, Saviour of the human race, was preserved free from every stain of original sin.
Luke 1:
28 And the angel being come in, said unto her: Hail, full of grace, the Lord is with thee: blessed art thou among women.
This verse was not interpreted by all early Christians to mean that Mary was conceived without sin, but it certainly was by some. Even if is not stated explicitly, this verse is viewed as Scriptural support for that understanding.
It also helps to understand the Doctrine of Recapitulation as expressed by St. Paul.
Ephesians 1:
7 In whom we have redemption through his blood, the remission of sins, according to the riches of his, grace,
8 Which hath superabounded in us, in all wisdom and prudence,
9 That he might make known unto us the mystery of his will, according to his good pleasure, which he hath purposed in him,
10 In the dispensation of the fulness of times, to re-establish all things in Christ, that are in heaven and on earth, in him.
St. Paul speaks of Christ remaking all things in Himself, the human race is given a new beginning in Grace, which is also why St. Paul refers to Christ as the "last Adam".
1 Corinthians 15:
20 But now Christ is risen from the dead, the firstfruits of them that sleep:
21 For by a man came death: and by a man the resurrection of the dead.
22 And as in Adam all die, so also in Christ all shall be made alive.
...
44 It is sown a natural body: it shall rise a spiritual body. If there be a natural body, there is also a spiritual body, as it is written:
45 The first man Adam was made into a living soul; the last Adam into a quickening spirit.
46 Yet that was not first which is spiritual, but that which is natural: afterwards that which is spiritual.
47 The first man was of the earth, earthly: the second man, from heaven, heavenly.
One of the Early Church Fathers shows how this Doctrine applies to Mary.
St. Irenaeus of Lyons, Adversus Haereses, Book V, Chapter 19:
Yes.
The short answer is that we pray (ask the intercession of) to the saints for the same reason that we ask other holy people on earth to pray for us.
We can ask the intercession of the righteous on earth, indeed there is explicit evidence from Scripture for this.
James 5:
16 Confess therefore your sins one to another: and pray one for another, that you may be saved. For the continual prayer of a just man availeth much.
It is my claim, and that of the Church, that there is no impediment to prohibit this asking of intercession from continuing among the saints in Heaven after they die. There are three arguements presented against it though, sometimes acting alone or in concert.
1) The saints in Heaven cannot pray.
2) The saints in Heaven do not care about the faithful on earth.
3) The saints in Heaven cannot be aware of our request for intercession.
If none of these objections are valid, then it is clear that the saints in Heaven retain their ability and desire to pray for us on Earth and can hear and respond to our requests for intercession. For there is enough Scriptural evidence to show that the righteous can intercede for us, this does not need to be proven, thus further evidence, either from Scripture or Sacred Tradition is not needed to support the doctrine, for it is clearly stated in Scripture provided that death provides no barrier to its continuance.
1) Can the saints in Heaven pray? Clearly prayer includeds praise and thanksgiving, two things which clearly are proper for a saint in Heaven. Saints offer constant praise to God in Heaven for they behold Him face to face. Intercession is also a part of prayer, and they would certainly be capable of this part as well as thanksgiving and praise, but the question arises whether or not they would use this ability, and that brings us to objection #2.
2) The saints in Heaven are clearly capable of helping the faithful on Earth, for as the Scripture states: the "prayer of a just man availeth much", and the saints in Heaven are certainly just and can pray. Would they exercise their ability to help us though? I think that the answer is clearly yes. All of the faithful in Christ make up one Body as the Scripture states:
Ephesians 4:
16 From whom the whole body, being compacted and fitly joined together, by what every joint supplieth, according to the operation in the measure of every part, maketh increase of the body, unto the edifying of itself in charity.
Thus the Body of Christ is united in charity, each of the parts care for the others. Is the arm indifferent to the health of the foot? No, but both are concerned with the health of the whole. Thus the saints in Heaven do care about and would help the faithful on Earth if they had the ability, which they do as argued in response to objection #1. For the saints are conformed to Christ, and has Christ loves all men and wishes them to be saved, for He, being the Good Shepard would leave the 99 behind and search after the one that is lost. So the saints care for Christ's flock because Christ cares for it. The saints would pray for us then even if they cannot hear us, because they know that we are in need of prayers and that their own prayers availeth much before the throne of God.
3) Can the saints in Heaven hear the petitions of the faithful on Earth? The arguement is that the saints are not omniscient and therefore cannot hear all of the prayers or indeed any of the prayers and petitions of the faithful asking them to intercede for them. Firstly, let us turn aside for a moment and look at the angels. The angels and the saints in Heaven both lack omniscience, for indeed only God Himself has that attribute. However, the angels can hear the prayers of the faithful on Earth, and the Scriptures even record instances when the faithful have addressed the angels and have spoken with them.
Psalm 102:
19 The lord hath prepared his throne in heaven: and his kingdom shall rule over all.
20 Bless the Lord, all ye his angels: you that are mighty in strength, and execute his word, hearkening to the voice of his orders.
21 Bless the Lord, all ye his hosts: you ministers of his that do his will.
22 Bless the Lord, all his works: in every place of his dominion, O my soul, bless thou the Lord.
Matthew 18:
10 See that you despise not one of these little ones: for I say to you, that their angels in heaven always see the face of my Father who is in heaven.
Revelation 8:
3 And another angel came and stood before the altar, having a golden censer: and there was given to him much incense, that he should offer of the prayers of all saints, upon the golden altar which is before the throne of God.
4 And the smoke of the incense of the prayers of the saints ascended up before God from the hand of the angel.
If the angels can hear the prayers and petitions of the faithful, why not the saints in Heaven? Neither are omniscient, both spiritual, and both in communion with God, serving before His Almighty throne. It is also fitting for their happiness to have news and knowledge of the fate of their loved ones, for the love that they bore for them on Earth, surely shall not cease when they are in Heaven, but has St. Monica loved her son St. Augustine on Earth, she will continue to love him in Heaven.
Truly the saints in Heaven can pray for the faithful on Earth. Truly they desire to do so. Truly just as the angels, the saints can hear our petitions and present them before the Throne of God. That is why Catholics pray to Mary and the saints.
Yes, the Catholic Church has always taught that "Outside the Church there is no salvation". Now, that phrase can be easily misinterpreted so I will explain exactly what we mean. But first of all, why do we say this phrase to begin with? As Christians, we know that Christ is the Way the Truth and the Life, and that no one comes to the Father except through Him. The Acts of the Apostles has a great quote.
Acts 4:
8 Then Peter, filled with the Holy Ghost, said to them: Ye princes of the people and ancients, hear.
9 If we this day are examined concerning the good deed done to the infirm man, by what means he hath been made whole:
10 Be it known to you all and to all the people of Israel, that by the name of our Lord Jesus Christ of Nazareth, whom you crucified, whom God hath raised from the dead, even by him, this man standeth here before you, whole.
11 This is the stone which was rejected by you the builders, which is become the head of the corner.
12 Neither is there salvation in any other. For there is no other name under heaven given to men, whereby we must be saved.
13 Now seeing the constancy of Peter and of John, understanding that they were illiterate and ignorant men, they wondered: and they knew them that they had been with Jesus.
St. Cyprian of Carthage explains the way in which the Early Church always believed the Church to be necessary for salvation and explains why.
St. Cyprian of Carthage, Treatise on the Unity of the Church, 251AD:
The question thus becomes, who according to the Catholic Church, is part of the Church that they may be saved? It is by Faith and Baptism that a person enters into communion with the Church. A validly baptized person is made a child of God and heir to Heaven, and the Sanctifying Grace lost by Adam's sin is restored. Baptism is absolutely necessary to be part of the Church. All of those who are unbaptized are lost. However, there are three kinds of Baptism, of water (the sacrament) but also by blood or desire. Thereby even the Incas before the arrival of Christopher Columbus had a chance to be saved, even if it wasn't a good chance. Just as Christ desires all men to be saved, He has esblished means by which all men have that chance. (You you wanted, I could go into this issue of Baptism more. I know that I am not explaining it much at all and it is important to the discussion.)
There are three bonds with which a person is tied to the Church, and we can us these and apply them to different groups to understand the Church's relationship with them.
1) Unity of Doctrine (Profession of One Faith received from the Apostles)
2) Unity of Worship (The common celebration of Divine worship and the sacraments)
3) Unity of Governance (Apostloic succession through the sacrament of Holy Orders, maintaining the fraternal concord of God's family.)
Only members of the visible Catholic Church under the leadership of Christ and His vicar on earth fully meet all three of these bonds of unity.
The Eastern Orthodox churches share Doctrine and Worship, but not Governance (They have apostolic succession, but do not recognize the primacy of Peter's successor among the bishops). Thus they share an imperfect communion with the Church and lack little in restoring their relationship to full communion.
The Protestant groups mostly share Doctrine, but there are significant differences in some cases, so this is not fully shared. Worship and the sacraments are only partially shared as the Protestants maintained Baptism (the most critical) and marriage among the sacraments, but deined the other 5 (for the most part, there maybe certain exceptions). There is almost no sharing of governance, the only possible thing that might pass as shared authority is the acknowledgement of the Holy Scriptures among all Protestants. Validly baptized Protestants thus share some communion with the Church by nature of Baptism, but it is a vastly imperfect communion.
A member of the Church, or a person sufficiently in communion with her though, while being a requirement, is not the same as being saved. Catholics can go to Hell just like anyone else can. What is essential to the issue is being in the State of Grace when a person dies. This state is entered into at Baptism, but can be lost by any grieviously sinful act (Technically, a Mortal Sin has three requirements, grave matter, full consent, and sufficient knowledge). No one can rightly jugde the state of another's soul, so a precise statement of who is saved and who is not is not possible, but whomever dies in the State of Sanctifying Grace (in communion with God and His Church in other words) is saved.