so I have gotten a fitbit watch from my old friend, he e-mailed them asking for replacement due to damage on wristband and they had send him a new watch, but he was able to keep the old one..so he has given me the old one that's still usable.

My question is..

is it possible to erase everything off it, create an account, and sync it with my account?
or do you think since they replaced it with the new one, the old one is block and it's unusable?