Attending a Catechism class at your local parish for however long they request (usually 1-2 years); then Baptism (if you aren't Baptized), Confirmation, and First Holy Communion at Easter Vigil.
The Church of England allows Catholics, and I presume others, to receive communion out of a "spirit of Ecumenism." Whilst they allow this, a Catholic should not partake of communion with any "church" which is not in communion with Rome; as to do so, is an explicit consent to the believes and teachings of said "church." Please see the link below for a full explanation as to why it is wrong for Catholics to receive communion in a Church not in communion with Rome.
I have never heard of a Marians Church. Do you mean Maronite? The Maronite Rite is in full union with Rome and a Catholic Church. Yes, you may receive communion.
The Melkite Greek Catholic Church is an Eastern Catholic Church in full communion with the Holy See as part of the worldwide Catholic Church.
No, it is not in communion with the Catholic Church.
Yes, a Catholic can marry a non-Catholic and still receive communion, as long as they are in good standing with the Church and have followed the necessary steps for a mixed-faith marriage to be recognized by the Church.
No, a Catholic should not receive communion in anything but a Catholic Church.
Some do and some don't if the apostolic church is a literal communion they do if they are a spiritual communion apostolic church then they don't.
No, the Church requires that a sponsor be a practicing Catholic. A person married outside the Church would not be in full communion with the Church and could not be a sponsor.
Yes, the Episcopal Church is part of the Anglican Communion.
It depends on the church. Some you can; others (like Missouri or Wisconsin Synod), you must be a member.
Yes, it is typically recommended to fast for one hour before attending mass or receiving communion in the Catholic Church.
No