A patch you can undo isn't a backup mechanism, it's data in the patch file when you download it. That's a big copyright risk. You could design a system that g

A patch you can undo isn't a backup mechanism, it's data in the patch file when you download it. That's a big copyright risk. You could design a system that generates undo info while you're patching. But it's easier to make a full backup copy of the original rom, and have no way to actually reverse the patching process.