Something just occurred to me. Aside from the Paragons, the other main characters only know about the pre-Crisis history and the events of Crisis because J'onn telepathically restored their memories. But what does "restored" mean? Logically, all he could've done was to share his own memories, which would mean they still wouldn't remember anything they did in Crisis -- or earlier in the original timelines -- that J'onn wasn't there to witness. Which would mean the Earth-1 heroes and Black Lightning would have forgotten a lot about their original lives. I doubt they're going to play it that way, though. They seemed to be treating it as if the people J'onn melded with remember everything -- as if he didn't share his own memories but somehow restored their own overwritten memories of the original history. That makes more sense from a storytelling standpoint, since you can continue drawing on the shows' past histories and don't have to constantly keep track of what parts J'onn J'onzz would or wouldn't have known about. But it raises more questions about how he could've done it. Well, I guess there's already established Arrowverse precedent for people regaining memories of an erased timeline. Cisco remembered being killed by Thawne after the timeline was changed to bring him back, and later I think he was able to vibe pre-Flashpoint memories, while Savitar and Alchemy were able to use the Philosopher's Stone to restore both the memories and the powers of people who'd been metahumans in the Flashpoint timeline. I guess we can assume that J'onn's Martian powers just happen to include the same ability (which the Arrowverse Wiki calls "parachronal retrocognition" in the article on Julian Albert/Alchemy).