I didn't think of it, but it's also a good riddle, although I couldn't be sure of the reward.
Not sure, but they only mentioned decoding it and getting 2.1BTC, I think it ready at an address.
Why not? they are promoting their exchange, keeping their payment promise will enhance their reputation
Yes, it is new, requires intelligence, it is difficult to find the private key. That's why i want to know if someone can decode it