Hmm, this is hard.
I'd make a alternate universe to simply be my playroom, since I'd be immortal, invincible and the like. What I'd do in that playroom, who knows. I mean, I could just stuff it up and do the whole process again and again, creating more alternates with alternates and breaking every rule of time and space known.
As for Earth, I'd transport people and animals of my choosing to a planet somewhere in the reaches of the universe, and then condemn the world to a solar light overload for a month, blinding/burning/killing the creatures of Earth, generally leaving it lifeless, assuming that it didn't burn to death.
As for the rest of our universe, in exactly 10000 years, I'd Big Bang it all over again, creating everything to my liking.
Woah, was that fun.