You should keep all the limit breaks. Besides Lionheart's not that bad.
It might be a good idea to upgrade the weapon though, unless you have some powerful magic junctioned to Attack or Strength or whatever it's called.
To spread rules you just have to play in different regions. If it doesn't change, play again. Eventually the rules spread.
What I'm asking about lionheart is if I skip the mid-level weapons, will Squall only perform rough divide and lionheart?
And how do I spread the all rule, like what town do I go to that has it so I can use it?