99 yards. it has happened 11 times in NFL history.
No. At one time, the college rule was a spot foul and the NFL rule was a 15-yard penalty. It is now the other way around.
The longest possible pass in the NFL is 99 yards (a touchdown thrown from within the 1-yard line) - it has been done 11 times in NFL history. (see related question)
Mark Malone caught the longest touchdown pass in Steelers history which covered 90 yards. It was thrown by Terry Bradshaw against the Seattle Seahawks on November 8, 1981.
The longest penalty in an NFL game is undefined. A defensive pass interference penalty is assessed from the line of scrimmage to the spot of the foul. If the spot of the foul is 30 yards beyond the line of scrimmage, the penalty is 30 yards. If the spot of the foul is 18 yards past the line of scrimmage, the penalty is 18 yards. If the spot of the foul is 9 yards past the line of scrimmage, the penalty is 9 yards. A defensive pass interference penalty is the only penalty that can be longer than 15 yards.
If the penalty is accepted, it is no catch. If the penalty is declined, yes, the pass attempt counts.
In college football, the penalty is 15 yards. In the NFL, the penalty is 10 yards.
In the NFL, the ball is spotted when wherever the pass interference penalty occurred and is an automatic first down. In NCAA football, the ball is spotted wherever the penalty occurred up to 15 yards and is an automatic first down.
In the NFL it is a 10 yard penalty from the spot of the foul. If the pass interference occurs in the end zone the ball is placed on the 1 yard line.
Defense Pass Interference (DPI) has not changed recently in the NCAA rules. It has "always" been a spot of the foul penalty, but not to exceed 15 yards from the line of scrimmage. So, if the infraction occurs 8 yards downfield it is an 8 yard penalty. If it occurs 52 yards downfield it is a 15 yard penalty.
In general, interference is a deliberate act, with contact, to impede a receiver from catching a pass...or an act by a receiver to prevent defensing a pass (offensive pass interference). It is most often hitting or grabbing the receiver before the pass arrives, or a receiver shoving a defender away. If the pass has not been thrown when a defensive penalty occurs, the lesser penalty of illegal contact will apply instead. The rules are different in each level of play (high school, NCAA, NFL), as are the penalties applied.
OPI is a 15yd penalty, against team A. It is penalized 15 yds from the previous spot, and a loss of down.