NO NO NO your first limitbreak for a level needs so many kills before it will get the second limit break. The second needs to be used so many times before it will learn a new one for a next level. As for the level 4 limitbreaks you need a manural item to learn those here are the locations for them.
Cloud - in the battle arena (its a prize)
Barret - after the train heads towards his hometown a person in the tent will give you it.,
Tifa - play a song at tifa's house to get hers
Aeris - trade in mythril to a man and choice the small box up the stairs
Red 13 - unlock the safe in Clouds hometown to recieve the item
Cid - go to an sunken ship when you have the submerine and seach it for his limit break, it has unknown monsters in the area
Yuffie - fight in this building where Yuffie grew up and you might get her last limit break item
vincient - find a cave with the sbmerine and visit on disk 2 and 3 with vincient in your party