returning inbounds...
 

A1 makes a fast break layup and ends up legally out of bounds. B1 retrieves ball and is in the process of throwing the ball inbounds. A1 (returning to the court from directly behind B1) deflects the pass [a] after one of his feet touches the floor inbounds [b] while still airborne (both feet last touched OB). (Obviously, [b] results in at least a ruling of A1 making the ball have OB status).

Ruling?

(Everything I found assumed all defenders start the play in bounds).

What if A1 hit the ball while it was still in B1's hands while the hands were over in bounds area?

A. Nothing. A1's inbound status makes this a perfectly legal play.

B. Tough to see this happening without a Intentional/Technical foul involved for contacting the thrower/the ball while in the throwers hands, but assuming neither of those happen it's an OOB violation, give B a spot throw-in on the endline.

C. If the defender has gained inbounds status and hits only the ball while the thrower is holding it through the boundary plane and over the inbounds area, then, the play is legal per a note in the section on throw-ins in rules book.

D. If the defender still has OOB status when he contacts the ball being held on the inbounds side of the boundary plane, then simply an OOB violation if the ball is knocked loose should be called and nothing if the thrower is able to retain control.

E. If the ball is being held on the outside of the boundary plane when touched by the defender, then a technical foul has occurred.

1. when A gets one foot down and the other is up in the air he does have inbound status. in your play i would still want to know where the rest of him is. the plane of the end line runs straight up to the ceiling. he can have inbound status but if his arm is through the plane or the leg is through the plane (while off the ground) and that helps him touch the ball i would consider a violation for breaking plane before ball is released.

2. if the thrower in holds the ball through the end line plane, over inbounds, the opponent can grab the ball from him, tie him up etc. legal but risky for opponent. if he hits the thrower in on the arm and you call a foul it is intentional by rule..

Has the throw-in pass been released when the ball is touched?

NCAAW has a similar case play. I'd apply the same general logic.

A.R. 188. A1 is inbounding the ball along her endline. A1 fakes a pass to
player A2, which draws B2 airborne in an attempt to intercept the ball. B2
lands out of bounds. A1 releases the ball with a pass to player A2 who is on
the playing court;
(1) B2 leaves the floor from out of bounds, breaks the boundary-line
plane and while airborne, touches the pass to A2 after it crosses the
boundary-line plane; or
(2) B2, while out of bounds, touches the pass as it is released by A1 but
before it crosses the boundary line plane.
RULING: In (1) and (2), B2 has committed an out-of-bounds
violation because B2 was last in contact with the floor when
she was out of bounds and then contacted the ball before B2
touches the floor inbounds.
(Rule 9-5.2.b, 4-23 and 9-4.1)
In (2), B2 touched the ball before it crossed the vertical inside
plane of the boundary line. This is not a technical foul because the
ball was being passed to a player on the playing court and not to
a teammate who was out of bounds such as after a successful goal.
(Rule 4-23, 4-10.1.g and 10-3.8)