Of course you can do that but in my opinion always moving all-in is not an appropriate poker behavior. Even if you have category 1 or 2 hands you have not the guarantee to win this round and especially in freerolls
it is rather more unsure because a lot of people move all-in with 72 or whatever and hit a set or two pair and you are out. So why should I take that risk? In freerolls it is better to play really conservatively. You have to be very patient and you should not spend to many blinds in "just watching the flop" because you will need it in later stages.