[ShadowHeart]

Rapps is the small dragon-like boss you fight in Wutai after Yuffie's stolen all your materia. It's Don Corneo's pet.

Lost Number is the boss in the safe in Nibelheim.. you know, you have to enter the right combination and the safe will open. After you beat him, you get the Odin materia and the key to the basement so you can get Vincent.

Materia Keeper is the giant spider-like boss in the Nibel mountains that you see on the screen and have to run into to fight.

Demon Wall is the demon wall boss at the end of the Temple of the Ancients.

And yes, the main character in FFIX is called Zidane in all version that I know of. I guess they just changed it some European translations (we don't get a Swedish translation of games in Sweden, thank GOD for that.. it's the same as dubbing a movie, horrible IMO).