I don't know about withdrawing to a credit card, but you are allowed to sell playmoney/accept transfers.
If you don't play real money with it before cashing out they may suspect a money laundering type scam or think you're using pokerstars
as a substitute for western union, which they don't appreciate.
I read about someone depositing then trying to transfer to make a purchase, and pokerstars wouldn't allow it because not enough poker had been played with the money.
...and of/c if you don't deposit, you will need to provide identification to cash out.