Held ball/Alt poss.
 

Team A has the arrow after a held ball. A1 reaches through the endline as if to pass or fake Defender B1 guarding endline. The ball is tied up between A1and B1 while the ball was across the endline (in bounds). I was told that team A doesn't lose poss. since the throw-in never took place, and would get the ball again for a spot throw-in. And since it took place in bounds no violation. However if he had fouled A1 while in bounds would it have only been a normal personal foul? I understand the various T's for out of bounds contact.

This situation is described in the case book (6.4.5 situation B). The ruling is "Since the throw -in had not ended and no violation occurred, it is still A's ball for an alternating-possession throw in. (4-42-5).

Rule 4-42-5 "The throw-in ends when the PASSED ball touches, or is touched by, another player who is either inbounds or out of bounds."

What you were told is correct :)

I believe (no rules book handy) a foul by B1 here would be a personal foul. I think if B1 reached across and fouled A1 OOB, it's an intentional foul (combined with the delay warning or T). If B1 reaches across and hits the ball, automatic T (and warning if the warning hasn't been given). Here's a hint; try to get the reach before the contact if you can.

I agree totally. Preventive officiating has always been a pre-game topic I like to discuss.