While it may be true that any kind of wish can be granted,Yes, Akemi Homura,to go back in time is somethingthat there is absolutely no way to do.You didn't say one word about wishing to travel back in time. You also didn't say where or how.You are only repeating your meeting with Madoka in your dreams.Besides... your wish was, "I want to be able to redo my meeting with Madoka."