This is kinda funny. I would e so friggin mad if I had a brother and he did that. But there is not way to undo like me I accidentally hacked and saved but I put the saved file different so I ddint overwrite my normal file. Then I did something stupid I saved the hacked file over my normal file so now I ave a almost beaten hacked game. But it made theg ame easier. I might suggest buying ur nephew a gameshark and turn on infinite strenght and health so he could be teg ame easier and faster and get back to where he was.