Are there any other requirements? So hypothetically, someone could just double his/her money and just leave with it? Also, what is the order of the promotion? Say, someone buys first but posts a screencap later than a guy who buys later, who gets the double? (Let's say there are only a few shares left.)
You can't double the money, because they are an IPO. You can double the shares.
Yep, that's what I said too

I can't guarantee you'll double your money, but I can guarantee I will double your shares as per the T&Cs above.