Can I buy a license without knowing the Challenge code ?
Yes, it is possible to purchase one or more licenses with an activation code without knowing or entering the "Challenge Code." Simply enter 00000000 (8x zeros) in the "Challenge Code" field, and you will receive two REGENs per license.
Thus, if you order two licenses, you will receive 4x REGENs (in your page “My License”) —enough to generate two sets of two "Response Codes" (just as if you had purchased two licenses and entered a "Challenge Code" for each).