1) Yes. The spell is still controlled by your opponent, you just change the target, which can be your opponent, because hexproof does not protect him from his own spells and abilities. And his spells don't have hexproof, so you can target those just fine.
2) If the creature is controlled by the same player as the Giant Growth (or their controllers aren't each other's opponents at least), then yes. Again, hexproof does not protect you from your own spells.
2) If the creature is controlled by the same player as the Giant Growth (or their controllers aren't each other's opponents at least), then yes. Again, hexproof does not protect you from your own spells.
Former Rules Advisor
"Everything's better with pirates." - Lodge
(The Gamers: Dorkness Rising)
"Any sufficiently analyzed magic is indistinguishable from science."
(Girl Genius - Fairy Tale Theater Break - Cinderella, end of volume 8)