Azazel promises to resurrect John so Mary can have a normal life with him if she gives Azazel permission to enter her house in ten years. Though Dean tries to intervene with the Colt, Mary makes the deal and John is resurrected while Azazel flees Samuel's body before he can wake up with no memories of being dead.

If you are asking what John said to Dean right before he died, he told Dran that Sam might turn evil because of what the Yellow Eyed Demon dod to Sam as an infant. He said if you can't save him, you'll have to kill him. 

Yes, it is legal to bet on multiple outcomes of an event or game. What is the risk? There is minimal risk involved when betting both sides. A user could make an error when placing a wager or the odds could potentially change while making wagers (try to avoid live games).

It's not illegal but bookies don't allow this usually as you get higher chances of winning this way. Or the ones accept it just lowers your limits or odds. Your best option would be to use different bookmakers for such things but they still have ways to detect those even.