yeah basically everyone goes to heaven in mormonism to my understanding. but there are like. multiple levels of kinds of things people may call heaven in the cosmology. and the most bestest kinds where you get to stay with your family as gods who make their own worlds are like exclusive to people who do the mormon thing properly; this requires a "sealed" marriage.
these varying levels of heavens are the degrees of glory and are split into the celestial, terrestrial and telestial kingdoms. that shit does not occur until after everyone gets resurrected though. until then people are held in like a waiting room type place called the spirit world, with those who have accepted jesus and are deemed virtuous get to sit in paradise. non-mormons and those who are Bad People get sent to something called the spirit prison where they are taught the gospel and given repeated chances to accept it. failure to accept this leads to the person being held in prison for a time after the resurrection. but it's a temporary thing, after which they'll be resurrected in the telestial kingdom.
there is one exception to this apparently which are the sons of perdition, which is a very small group of people. this includes the pre-mortal spirit followers of satan. as well as mortals who deny the holy ghost after being presented with a personal witness and perfect knowledge of jesus christ.
the posthumous baptism thing is done as part of the initial judgement involves whether or not someone was baptized by someone with the correct credentials.
thank you for the mormon lore dump, it's informative and less rude than asking an ex-mormon about their religion by going "i saw a tumblr post about your old cult, why do they bother?"
