Im sure its been asked here before, but im to lazy this morning to go through 20+ pages

i know you can forfeit the bonus anytime you want but,
If i deposit $100 and get 50% bonus and have $150, do i start playing with the bonus funds or the real money? what i mean is if i hit it big before im down to $100 can i forfeit bonus money only not winnings or is it after ive played $100 i can forfeit the bonus money only ?
Or can i forfeit bonus anytime i want without losing winnings ? if im down to $10 and still have wager to do and hit a 1000+ and want to forfeit
would i miss all winning or just bonus funds of $50 ?

hope it not to complicated this early in the morning