Do you want just to unregister or Roll back? I think you have to Roll back to unregister from beta labs.
And you know the consequence of Roll back that it will erase all your data.
By the way why do you want to unregister we need more sensible people like you to find more bugs on the beta update. :)
Yes of course it will be associated with your google account or IMEI no. as long as you are registered to their program.
The google account and IMEI no. that you used to get the beta update.