This update would add new levels and new characters. And by characters I mean Tails, Knuckles and Eggman. Yes, you would be able to see what happened to them before the main part of the game.

Here are some screenshots:

But yeah, that would basically be it. It's a shame this update will never be released, but oh well, it happens sometimes.

Maybe I will finish this update, and I say maybe, because it's very unlikely to happen, but even then, I would need some help with it.