I've been refreezing mice and rats for years. I only refreeze once. The refrozen mouse/rat is offered to a snake that I KNOW will eat it.
As far as food size goes, my baby bps got adult mice after just a few feedings of hopper mice. Once the snakes got to 300 grams I started giving them small rats. My bps that are about six months old are eating 40-50+ gram rats.