Well if you're playing the U.S. version of KH you won't be getting 'Deep Dive' That's for KH: Final Mix. You will get a trailer though.

The requirements are: Locking all the worlds keyholes (Including Winnie the Pooh's book), Beating the Hades cup tournement, and finding all 99 Dalmations.

Now if you imported Final Mix. I'm not sure if the requirements are different. I'd have to look it up.