We are all equal before the eyes of the Lord.
Seemingly, the only premise needed to obtain the Kingdom of Heaven is to take Jesus Christ as your Lord and Savior - to believe he existed, died for our sins as living sacrifice then was resurrected on the third day to ascend to the right hand of God and realizing that only through taking him as the sole means of salvation from sin can we receive atonement and go to heaven.
I am not clear on the need for baptism by water to enter the kingdom of Heaven, unfortunately. If anyone can help me on that, please do. My current thoughts lead to the idea that if one is not baptized by water, you may still go to Heaven.
In tension with salvation by grace through faith is doing good works after you have been justified. Our fleshly vessel, which contains our soul, receives into it fully through the rebirth of ourselves into a new life walking with Christ the Holy Spirit.
We are not freed from the commandments and the law, but guided by the Holy Spirit and reborn via our faith, we are expected and do naturally walk ever more toward sanctity through our relationship with God.
If we backslide and disbelieve after the above events have happened, some argue that the spirit will never let you fall back to your old self before the rebirth.
My current thoughts are that if that were the case, you are pushing the point of judgement to the time of salvation, not after death. In so doing, you are losing free will in the process by becoming a puppet of the Holy Spirit.
I think if we backslide and disbelieve and do not walk in the paths of righteousness, we can lose our ticket to Heaven.
However, unlike much of what you write in the above, I do not think there are degrees of expectation in ones salvation - you are either saved or not by grace through faith. If you have not received the good news, that makes it pretty hard to be saved, so it is all of our duties to help those who have not been informed hear the good news and at least have that chance. But I cannot see that knowing less or more makes it harder or easier for you to be saved by some kind of sliding scale standard.
However, the idea of teachers and leaders in faith being held to a stricter standard of word and deed is clearly spelled out.
One thing I would add about the need for studying and agreeing to or discussing a catechism or taking a class as a prerequisite to Baptism can be indicated by the following:
Acts 2:40-41 (NIV)
40 With many other words he warned them; and he pleaded with them,
“Save yourselves from this corrupt generation.” 41 Those who accepted
his message were baptized, and about three thousand were added to
their number that day.
Obviously, 3000 people could not have heard the word, accepted God's message and been baptized all within one day if they had to do the catechism thing. Would not the original Church on its birthday and its practices which were under the direct supervision of the original 12 apostles who were actual eyewitnesses and companions to Christ himself be more authoritative than any additions made later in a more modern Church that have been added on extra-Biblically?
In the end, though you are seeking an answer within Catholic doctrine, maybe your answer lies more with Scripture?
All this is just my current understanding born of reading Scripture, both individually and in community, tradition, reason and my own experiences.