fire protection in vessel?
Take the door knob off the other side and keep it in your pocket.
It is very easy to replace a standard knob set with a bathroom knob set that locks. The problem is going to be getting your parents to allow you to do it or to not remove it if you don't ask.
It is impractical and unimaginable and the vagaries of your fancies cannot be executed.
I use it when travelling, as it keeps your door from being opened, even a little bit. You put the L shaped end into the strike plate in the door frame, close the door and slide the locking part up against the door. The door won't budge.
