sustain focus, can it sustain any spell?, need some book ninja fu Options

[Akai Sokata]

Ok scope this. I was GMing as usual and one of my players picked up a sustain focus. he knows levitate so he locks it in at a force four with a target of himself. so does that me he always levities as long as he holds it?.

and a few more things about levitate? this one happened a few sessions ago, but another player of mine lavitaed a smug out the hands of some street garbage ganger. then proceeded to aim and cast another levitate on the trigger of the gun blasting it off in auto fire at the poor frager that got it stolen from him. don't worry about time this was over the course of three turns.

so the question is can levitate man a target, or can two levitate spells be cast on the same target.

as always pardon my spelling/grammar. im still a idiot