I don't know if this has been posted before but I haven't found any threads talking about it, but my cousin and I discovered that if you can go to hell difficulty, lets say your in act 1 hell mode not any farther(dont know if it will work for any other difficulties), but lets say you arent past act 1 hell mode, or act 2 w/e, you can go to NM difficulty and join a later act or quest, leave the game and for your difficulty(hell mode, or any other difficulties)that later quest you actually havent got to you can do in hell mode now