So..

Ms. Marvel skrull has stealth, plasticity, hypersonic speed.

Can i turn off JUST stealth? or do i have to turn off the entire thing?

Breaking away.

CXD

C and X are allies, D is enemy.

C is a flier and X is grounded, when C carries X, does X have to roll to break away?

You can choose to not use the Stealth part of her power, but then your opponent can also see you.

No, X doesn't need to roll breakaway.

but do remember that at the start of your opponents turn it is reactivated.