Okay, Limit form requires NO other party members. It takes up four Drive bars. It's max level is 7.
It's four "shortcut menu"(L1) attacks are:
Square: Strike Raid - Sora throws the Keyblade having it return. It can be repeated multiple times.
Triangle: Ars Arcanum - Sora attacks with boosted speed and strength. It starts as a ground combo, then gives you the reaction command Bash allowing you to do a more powerful finisher
Circle: Sonic Blade - Sora closes in on the target with a guard breaking attack. It gives you the reaction command Rave allowing you to go back and forth several times and then it leads into a finisher.
X: Ragnarok/Ragnarock - Sora does a quick air combo then you get a reaction command allowing Sora to shoot energy from his keyblade.
Other Abilities:
Sora can dodge roll, each level up makes the roll faster. To use it press square. It can be used in regular form if you -tap- square. (Holding it makes you quick run)
Sora has an improved block, just tap square while not moving.
Sora has Stun Impact, after you land a combo, this is one of the finishers. It is great help as it sends all the enemies it hits into the air.
While in Limit Form the only way of leveling up the form is to land a finisher using one of the Shortcut menu attacks. Example: Sora does Sonic blade, keep pressing triangle until you can't press it any more, that's one EXP.
If you have an item equipped in the Shortcut menu, it over-laps the special attack making it unable to be used. Example: You have megalixers on Square, you can only use those megalixers and you can't use strike raid.
It's a really fun form and using it makes fighting ES on critical mode somewhat easier.
Helping yah?