2) Having 52 different earths does not address alternate timelines, as hypertime did. For example, All-Star Superman and Whatever Happened to the Man of Tomorrow seem to both be alternate splits from the timeline of Earth-1 Superman. (The latter future Superman appeared in Superman/Batman issues, and therefore must exist some...when?) Likewise, there are the Earth-1 timeline splits of Kamandi's future vs. the Legion's future.
I'm pretty sure the Kamandi/LSH discrepancy was actually fixed in a Maggin story somewhere. And I think it even had something to do with that future costume that the Apes were hanging on to.
A lot of people seem to have forgotten that "Whatever Happened to the Man of Tomorrow?" was an
imaginary story. Like the original "Death of Superman," "Superman Red/Superman Blue," and those crazy stories where Luthor was Kal-El's father, or Superboy was Kara's nephew,
it never happened. That was the whole point! It doesn't need to be accommodated, explained, or incorporated. If Jordan Elliot has started showing up in other comic books, it's a misunderstanding and the last holdover from the Hypertime fiasco and should be forgotten.
All-Star Superman isn't really a split from the Earth-1 Superman, it's a split from the modern Superman. It's the modern Superman where Crisis never happened. Pre-Crisis, Superman's continuity slowly evolved over time instead of being rebooted. So this is a "what-if," an extrapolation on the idea that Superman's exisiting continuity had continued to evolve from what it was in 1986 to today, with no reboot ever tossed in.