A personal foul is a dead-ball foul, which means the 15 yards are always added on to the end of the play. So the marker (and the new line of scrimmage) will be 15 yards beyond where the ball was spotted at the end of the play.
A fumble is down when the recovering player is down or when the ball goes out of bounds...so yes, if the ball is fumbled forward and recovered by the offense, or goes out of bounds, past the first down marker, it is a first down. The exception is on fourth down. In the NFL, only the player who fumbled the ball can advance it on fourth down.
Yes. Regardless of whether the penalty yards would be enough for a first down, any personal foul penalty on the defense results in an automatic first down for the offense.
A first down is gained when the offense gains ten or more yards.
NFL use red.
As long as there was a clear change of possession to the defense before they fumbled the ball back to the offense, then the offense would keep the ball and get a new set of downs. If the defense fumbled the ball back to the offense without ever establishing possession, then the ball would go over to the defense on downs. The only way the offense could retain possession in this case is if the ball ended up beyond the first-down marker when the offense finally recovered.
The only time the offense would decline that penalty, would be if the resulting play advanced them more than 15 yards down the field. Either way, they would have a first down.
YES, THEY JUST REPLAY THE DOWN
You probably cannot, although you may try to plead it down to a lesser offense.
September 1998 was when ESPN first introduced it in a pro football broadcast.
In American football, a team gets 4 downs to reach either the first down marker or the end zone. In Canadian football, a team gets 3 downs to reach either the first down marker or the end zone.