Super-Boy Prime is Clark Kent from an alternate universe, Earth-Prime, which is "our" universe. He comes to Earth-1 and eventually New Earth, but doesn't like how things turned out so he turns into a bad ass evil brat who FSU
The Anti-Monitor is basically an evil God from the Anti-Matter Universe. He is the ultimate evil within the DCU.
No it's not. That would be impossible.
Not at all. Though there are similar elements from Post-Crisis DCU brought over.
LOL not even close.
Pre-52, aka Post-Crisis Timeline, only had about 25 years of continuity but it heavily relied on Silver Age stuff to an extent.
No, no big 2 character is one big connected story and arc.