foul- player control, during and before shot

[Kelvin green]

Lets see how bout we go to the basics

Ball is dead when there is a player control foul or team control foul.
Team control ends when the ball is in flight during a try or tap for goal..

If the team control happens A cant score. If the foul happens after the ball is inflight the foul is a non-team control foul and does not cause the ball to become dead immediately

in your 2
if A2 sets illegal screen before the shot ball is dead
if A2 sets illegal screen during shot the ball is either released or not. If not released it is before the shot.
if it is after the shot A1 is either airborne or not. If airborne two have two fouls, one on A2 and one on B fouling the shooter...
After the shot and not airborne, common foul on B common foul on A

You get to sort out the penalty