I got an e-mail from BRG dept confirming the free night. The e-mail looks different than the previous e-mails I received from them:
Please be informed that the Free Night is subject to the hotel’s regular cancellation policy as described below:
'A deposit for the entire stay is due at time of booking. Canceling your reservation or failing to arrive will result in forfeiture of your deposit. Taxes may apply.'
The fact is that if it's free, why should there be a deposit?