To me there seems to be some discrepancies about the rate of aging of the four. Lois and Alexander seem to be much older, Superman and Superboy-Prime about the same age as when they entered "Paradise".
Well, there you have it: the two that have superpowers have aged much slower, possibly because of their superpowers and superpowered metabolism, which presumably takes more from the food they eat and retains water and in general breaks down a lot less. Superman may or may not be immortal, but it makes sense that he (and someone with his powers, like Superboy) would age much more slowly.
On the other hand, Alex has no superpowers, whereas Lois is a normal woman that, it should be added, has been ill. Most older people when they're sick appear to be much, much more aged.
And what kind of Paradise would it be where the retired heroes can see what a mess the world has become? I also remember that "Paradise" was actually a pocket dimension only accessible by Alex's matter/anti-matter powers. Where did the crystal barrier come from? GA Super-man busts it open with physical force?
Good questions, actually. I really hope they resolve some points about the dimension that Earth-2 Superman is placed in.
Maybe these four are not who they seem?
Nah, no way. They have the big surprise reveal of Earth-2 Superman returning, and suddenly they pull the rug and say, "ha ha, we tricked you!" Something like this is too big to possibly end in a "fakeout."