In 1, we kinda need to know when the clock expired. If time had expired before the ball was touched by A88, then, indeed, the period is over, and the penalty would be enforced at the 3rd period kickoff.
However, if it was during B21’s apparent ‘run,’ then the period didn’t actually expire, since the ball was dead at the moment the ball was touched by A88. With replay, the RO can identify the time remaining when the ball was touched and became dead. Then Team B would get a ‘series’ at the previous spot, after a 15 yard penalty, and the game clock would start on the snap, with a 25 second play clock.
Without replay, we gotta hope somebody on the crew would have an idea about the time remaining.