All of the Duelbits reward doesnt have a wagering requirements after fulfilling the requirements to get it. I claim promotion like this before and I remember that you will receive all the profit from the free spin directly to your wallet which is instantly available to withdraw.
They have already set a wagering requirement of $100 to get the free spins so yes there would be no such after requirements if you want to withdraw the money I think.But you have to risk $100 also but if you are getting 50 free spins then it's worth trying it if you are gambling so take the risk and who knows you get some good profits into your account.