1st to say, nice puzzle, thx for trying new stuff.
2nd to say sadly very many cannot enter as they are unable to validate emails on the forum and so cannot input onto the forum. This is why BB moved away from voucher codes too at a guess. Not sure what the solution is, if any.
Son tried to change his email for game via support, was told needed to sort with Uplay/Ubisoft, and yes they told him he needs to sort via BB support.