the lvl 4 limit breaks are earned differently.

Cloud-Omnislash: Earn 35,000 BP ate the GS battle arena.

Tifa-Final Heaven: Go to Tifa's house in Nibelheim, play this tune on the piano upstairs. X, square, triangle, L1 R1 + triangle, L1 R1 + square, X, square, triangle, L1 R1 + X, square, triangle, L1 R2 + X, O, X, square, X. Then exit it for the lvl 4 limit.

Aeris-Great Gospel: Go to the cave over the lake near Mt. Condor. talk to the man until he says you have been in __ battles. go outside and fight monsters until the last 2 numbers are the same, 0011, 0022, 0033. Then go back and talk to him again and he will give you and item. Take the item to the house outside GS and tell the man you want the item in the upstairs box. Open it for Great Gospel.

Barret-Catastrophe: After you stop the train go to one of the tents and talk to a lady and she will give it to you.

Red XIII-Cosmo Memory- Go to the safe in the Nibelheim mansion, the safe is in the upstairs left room. Enter in the combanation without going 1 over the numbers, 36, 10, 59, 97. You will fight the Lost Number. After you beat him you will get Odin, Cosmo Memory, and be able to get Vincent in the basment.

Cid-Highwind: while in the sub look for a red, sunken plain in a corner. Go inside but be careful there are annoying monsters in there. Go in the first door and go downstairs and open one of the chests (By the way just in case you dont know, yuffies ultimate weapon is in the downstairs upper left, hidden by a pipe).

Yuffie-All Creation: Go to the Padoga in yuffies home town, fight all the bosses and you will get All Creation and Leviathan.

Cait Sith-Slots: defeat 50-100 enemys.

Vincent-Chaos: Go to the waterfall in the sub in disk 1 with vincent in your party, then return on disk 3 with him in your party and open the chest, you will get his ultimate weapon and Chaos.

Well thats all of them I hope they will help you.