First off...

Hurricane Kick:
E Discard 1 momentum (6+): If this attack deals damage, your opponent's control checks get -2 for the rest of this turn.

What dose the (+6) mean or refrence?

Secondly...in standard play is the promo set SF7P Legal? It has a 4 pointed shurikin...so I thought so...just making sure.

The (+6) means that in order to activate the ability you have to make a control check against a difficulty of 6. You can commit foundations to pass this check.

The characters of SF7P are legal to play if they've been released into the prize support (not sure if Blanka has), since all but Cody have 4-point shurikens. When Set 12 releases next month then Cody will no longer be playable, the others from SF7P will be though (again, if they haven't been released into the prize support they will only become legal when they are).

Stamp for Cascade. Good catch with Cody! Blanka has been in the standard prize support, as a note.