Throw-in/Backcourt violation?

[Zoochy]

I still have a thought on the 2nd play...

(2) Throw-in for Team A near the division line in their backcourt (Team B’s frontcourt). A1’s throw-in is deflected by B1 who is applying direct pressure on A1. B2 jumps from their frontcourt, catches the ball in the air and lands in the backcourt.
BktBallRef says...
LEGAL. The rule allows a defensive player to leave his FC, catch the ball and land in his BC.
I am not 100% sure that B2 is a defensive player. Here is why.
There is no defination for offensive or defensive player. The only time I see the word 'defense' in the rule book is in reference to a player on the team that is not 'in control' of the ball.
Block/Charge 4-7-2a. A player ... with the ball ... avoid contact if a defensive player .....
Free Throw Administration 8-1-4a. Marked lane spaces ... four defensive and two offensive. When A1 has disposal of the ball for free throws there is player and team control.
So my point is that there is NO team control during a Throw-in. Thus when B2catches the ball after it had been deflected by teammate B1, he has now established player/team control from a loose ball. Since B2 has Frontcourt status when he jumps and catches the ball and now lands in backcourt, backcourt violation occurs.
In conclusion, the only legal play would be play 3, because 9-9-3 would still apply. B2 has caught a throw in with both feet off the floor after leaving his frontcourt.
WOW... think about it and get back to me. OK?