Kids and Trolls escaped the Scratch by fleeing into Paradox Space/Beyond the Forth Wall.
The new Earth dosn't seem to be "Alternia with humans". My personal theory is that the first time around, a Universe gets a benevolent animal guardian like Bec, if that fails to produce a sucessful session, and the universe gets Scratched, then Doc Scratch (or somebody similar) is the first guardian, nudging history to better prepare the players.
I don't think it's going to be a carbon-copy of Alternia, but it will be harsher, or at the very least there will be an increased focus on Games.
The Kids/Guardians role will be switched. John will be Nanna's guardian, Dave will be Bros (Hence why SbaHJ is now a Movie, Dave is an adult in this), Rose will be Mom's guardian (We saw some of Kid Mom's science labs), Jade is Hass's Grandmother.
Also, I am sad to see that Jane Crocker has missed the greatest Mustachioed Funnyman of all time: Groucho Marx.