Why would someone would give you 12 BTC and give condition that you need to pay $1000 first before you can withdraw it??  That action is classic scam and they are just fooling newbie to fall on such scam attempt so don't be so greedy thinking about that 12 BTC since everything with that is fake.

You better save yourself and don't feel sorry that its missed opportunity for you since there's nothing to get there as those scammer just want to get your money then will left you behind. Just do further more research about it and also listen to people who post their opinion about your questioned ask in this thread.