A)the head coach may leave the coaching box to go to the scorers table to rectify a scoring mistake only if beckoned by an official! false, correct?

B)the head and assistant coaches may stand during the 30 second interval permitted to replace a dq'd player! False, only head coach correct?

You are correct on both counts. Rule 10-5 article 2.

Z

1) Legal as per R10-5-2.

2) R10-4-4 sez the assistant coaches gotta sit. Reason? The replacement period is NOT a charged time-out per 10-4-4(c).

ART. 2 . . . The head coach and assistant coach(es) must remain seated on the bench at all times while the clock is running or is stopped except to:

a. Confer with bench personnel and players within the confines of the bench area during a charged time-out or the intermission between quarters and extra periods.
b. Attend an injured player when beckoned onto the court by an official.
c. Rise in front of their seat to spontaneously react to an outstanding play by a member of their team or to acknowledge a replaced player(s), but must immediately return to their seat. (See 1-13-2)

Isn't that from last year's book?

The assistant coach doesn't even show up in the book this year!!

Yup, they re-wrote R10-5-2 this year.