#1
I'm new but an extremely fast learner, and have gotten stuck on a song. Maybe I have the wrong idea here but this looks like a pull off to me.
Tab 20 I see as two pull off's to an empty note. But on tab 22 you have the same thing but from an open note onto an empty note?
#2
They are "ties" not pull offs.
The half note has its duration extended an eighth.
#3
Bar or measure 20 and 22, not tab. Incidentally it's badly written, it should be an eighth note tied to a half, not the other way around.