Watch out when on the team he takes over the person in the 3rd slot and if you move him around other people become sephiroth.
When sephiroth is on the gold saucer or other places like that he is invisible and if your main character is now sephiroth it may muck up your game.
Nibelheim and go to the library and it will show how
Cloud got the big sword and how he became a mercenery.
Battle Arena and earn 32,000 points, these can be exchanged for Cloud's Limit Break