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Type in Kingdom Hearts, go to it, hints and cheats, scroll down to FAQ/Walkthroughs. Find one of the larger ones. I think it is by ElectroSpecter or something. In that guide there is a chart that tells you not only about the dream weapons but when you answer Wakka/Tidus/Selphie's questions. And yes, they all have an effect on the difficulty and rate of leveling up and stuff of the game.