Dead Ball? NFHS

[Zoochy]

R1 hits the ball that is traveling towards outside the antenna (Net pole standard). Can a player pursuit outside the court, but still within the playing area, cross the centerline and play the ball back into their side of the court? When does the play become dead? When the ball breaks the imaginary plane of the net? When the ball completely crosses the imaginary plane of the net? Or play-on, legal play?
Does it matter if the ball is above the height of the net? Or below the height of the net?
Please provide Rule Reference if possible

[Zoochy]

I have found the rule(s). 9-5-8 is the best. Ball is dead once it completely crosses the vertical plane of the net extension. Also rules 2-3-1c, 9-3-3a, and 9-5-2 all state the same explaination.