((Ok since I've become the "backstory guy" somehow, here's what I had in mind about the planets and our past and all that. The planet which Pyro burned down was originally intended to be some planet in the distant past, not the one before this one, or even before that, but since everybody suddenly kind of wen "oh hey the last planet was burned" then I just rolled with it. I mean, sure, no harm done there, right? Now, about the "failed planets", I think it'd make sense if we leave a planet once it fails. The planet on which we are right now was a brand new planet in my mind and we were gonna give it shape and develop it and if that didn't work, then we'd just move along.
About the memories, yeah, anyone who made it out alive from the burned planet had significantly more memories still there than the ones that didn't.
That's just my thoughts and all, feel free to suggest adjustments or make corrections or something. And I'll get my RP post up soon enough, just really tired atm))