In addition to the above questions:
What type of verification process process is required ? ( Better if it does not involve any personal document)
What type of game? Multiplayer, gambling, lottery ?
Yes, there is no way that they will give away $20 and let you just withdraw it. I think even if they ask for your KYC it is still unlikely you will be able to just draw an already listed token. There must be some sort of catch.
There has to be something else you have to do. I certain trade amount you have to reach or something. Now I wonder if the OP will come back and answer all this?