UO Second Age

I'd like to ask does it (snooping) have any increase of the chance to successfully steal an item or the weight of the stolen item, or all it does is peeking chance. Or reduces the chance to be noticed? Generally do you guys know in which calculations does it participate?
And 1 more thing. Is it possible to take someones mount in the town, i mean to lure it somewhere or something like that.. Or to take it from him while he is gone..

Snooping allows you to open the main pack, you need to open other containers after that individually with snooping...so you can target steal. You don't need snoop to steal if you do it on the run but such an act is called a random steal. In other aspects it doesn't affect stealing at all.

One more question about the thief, if someone attacks him in town, or out of town and they run to a guard zone if the thief writes 'guard" will they help him? (that's in case he hadn't stolen anything since his last death) Or he is freely attackable everywhere even in town

If you arent grey or perma grey you are under the protection of the guards. Outside of town remember you cant give counts and some people who know you are a thief may kill you on a whim.