Do you all the drive forms have to be completely leveled up to get Final Form in Kingdom Hearts 2?

Answer 1

No;

The final form is a form that can only become available near the end of the game, after you've reached Memory's skycraper in The Word That Never Was. Sora changes into Final Form by chance, meaning that it simply "happens" when you attempt to change into one of the other Forms. It has nothing to do with the levels of your other forms. From the moment you've changed into it once, it will become routinely available via the Drive command.

Tip: A good way to get the final form: change continuously into your other drive forms in the Olympus colloseum. When your drive bars are empty, enter a cup at the underdrome to fill them up again and start over.