Cagli

I don't need more than that. I can just edit the .plist file and add any number of keys of gems or anything

I think I found a way how it does work! Make a backup of your game, uninstall the game. Install it again, then either use this hack (or your own edited file), upload it, and start the game... Edit: Confirmed. got 2000/20000 energy and 5000 gems.

I signed out from gamecenter, turned Airplane mode on, closed the app completely, deleted the cache folder. Nothing works. My old game just returns with the same amount of gems, etc.. I don't know how they do it, but Cut the Rope had the same thing.

Yeah, does not work. Closing the App completely, replacing it, opening the App again just instantly recovers the file somehow. Has something to do with GameCenter i guess...