13. A–1 is erroneously awarded a one-and-one. A–1 makes the first free throw. A–1’s second free throw hits the rim and as B–1 is rebounding the ball, B–1 is fouled by A–2. The error is now recognized. Official cancels the free throw and cancels the common foul. Is the official correct? They say No! What aspect am I missing with this. I thought you could cancel hoop and related activity!

What you are missing is that the last foul did not happen during the free throw. It happened after the free throw ended. See 4-20-3.
Therefore, the official should only cancel the point for the unmerited free throw, but not the rebounding foul. Continue the game by awarding team B the ball out-of-bounds if they are not in the bonus or by shooting free throws at the other end if they are in the bonus.

Damn...yup...gotta read carefully. Thanks!