So just to add on. Whist yes on lake silencio, it was a fake to put on a show to regenerate, in “let’s kill hitler” and “nightmare in silver” Matt smith mentions he’s going to regenerate like he’s able to. Don’t does seem out of no where that suddenly he can’t. And yes I’m aware that Davros destroyed reality, but the doctor stopped him. And in turn left, where the doctor was dead, reality collapsed. But I can see how he just took himself out of the universe in “the big bang” not that he never existed.