If a referee signals a goal before the ball has passed wholly over the goal line and immediately realises his error, what action should he take?

Play is restarted with a dropped ball.*

A neutral assistant referee signals a player is guilty of violent conduct. The referee sees neither the offence nor the signal and the offending player's team scores a goal. He then sees the assistant referees' signal. What action does the referee take?

As long as play has not restarted, the goal is disallowed, the guilty player is sent off and the match continues with a free kick.*

A goal is scored. The referee then notices a signal from his assistant referee. The assistant referee tells the referee that a few seconds before the ball entered the goal, the goalkeeper of the team which scored the goal punched an opponent inside his own penalty area. What action does the referee take?

The goal is disallowed, the goalkeeper is sent off for violent conduct and a penalty kick is awarded to the opposing team.