Sonic 2 Unimpossible started out as a joke hack. I was screwing around and made it so that you gain a life every time you die, you can't drown, and you don't need rings or emeralds to go Super (and it doesn't consume rings). Needless to say, this was all just for the lulz. And it was good. But then I realized it was impossible to get a game over (hence where the name of the hack came from), and being Oppositionally Defiant, as I am, I was determined to get a game over in the un-game overable game. So I did some more hacking, and now here we stand. The current concept of the game? Everything listed above.
But you might ask "Wait, doesn't that mean it's still impossible to get a game over?" No. See, the game runs on 8 bit hexadecimal. What does that mean? It means there is no number larger than 255. It basically means that 256 = 0. Now I've made the hack so that in addition to gaining a life every time you die, you gain a life for every ring you pick up. By this method, you get 256 lives quite quickly. Now recall what I said: 256 = 0. Because of its 8 bit programming, the game automatically resets your life count to zero once you have 256 lives.
Initially, this didn't give you a game over. You could have zero lives without getting a game over. This is because you're not supposed to be able to have zero lives without dying, so the original game only ran a game over check upon dying. I rewrote the game over subroutine and added a branch to it in Sonic's main routine, so that every frame it checks if you have lives, and if you don't, your game is over. So now, having 256 lives is the end for you. And believe me when I say that it makes the game incredibly difficult.