Kingdom hearts chain of memories gba... unlock?

So I beat both Sora and Riku's story mode and saved before the final boss but for some reason I don't think the game unlocked anything. First of all, from what I heard, after I unlock the game, 'theater mode' is supposed to be in the menu, but it's not there. I restarted the game using another file so I could get ultima weapons and other unlockable items but I'm not sure if my game has a glitch or what. How do I unlock the game? Or like how do I check if my game's unlocked?