2-4-1 In PlayPic A, the airborne receiver is contacted so that his forward progress is stopped. When the defender carries him out of bounds (PlayPic B), the result is a completed pass.
2-4-1 In PlayPic A, When an airborne receiver is contacted by a defender (PlayPic A), causing him to make first contact with the ground out of bounds (PlayPic B), it is an incomplete pass. The game official's judgement regarding whether A1 would have landed inbounds is not a factor.
2-4-1 A catch is the act of establishing player possession of a live ball which is in flight, and first contacting the ground inbounds while maintaining possession of the ball. Because the player's foot is inbounds when he grasps the ball (PlayPic A), and maintains possession after the contact and the landing out of bounds (PlayPic B), it is a catch.
2-4-1 The airborne player grasps the ball (PlayPic A), but after the contact by an opponent (PlayPic B), he lands out of bounds (PlayPic C). That is not a catch.
2-4-1 No catch. The receiver does not have possession of the ball inbounds when he comes down. When there is possession, the first foot to touch the ground determines whether it is a catch - as it must touch inbounds, even if the other foot then touches out of bounds. If the feet touch the ground simultaneously, both must be inbounds.