Tried to edit the strike-throughs out on the post above but time ran out. Going to try again here without posting the links which are in the post above or using spoilers.
SECTION 18. Encroachment and Offside
Encroachment
ARTICLE 1.
After the ball is ready for play, encroachment occurs when an offensive player is in or beyond the neutral zone after the snapper touches or simulates (hand at or below his knees) touching the ball before the snap (Exception: When the ball is put in play, the snapper is not encroaching when he is in the neutral zone).
Offside
ARTICLE 2.
After the ball is ready for play, offside occurs (Rule 7-1-5) when a defensive player:
Is in or beyond the neutral zone when the ball is legally snapped; Contacts an opponent beyond the neutral zone before the ball is snapped; Contacts the ball before it is snapped; Threatens an offensive lineman, causing an immediate reaction, before the ball is snapped (A.R. 7-1-3-V Note); Crosses the neutral zone and charges toward a Team A back (A.R. 7-1-5-III); or Is not behind his restraining line when the ball is legally free-kicked. Offside occurs when one or more players of the kicking team are not behind their restraining line when the ball is legally free-kicked (Exception: The kicker and holder are not offside when they are beyond their restraining line) (Rule 6-1-2).
American Football Rules IFAF Approved Ruling 7-1-3:V
V. A66, a restricted lineman between the snapper and the player on the end of the line, or A72, a restricted player on the end of the line of scrimmage:
Lifts a hand or hands from the ground immediately when threatened by B1, who is in the neutral zone. RULING: Blow the whistle immediately. Team B dead-ball foul,
offside. Penalty — Five yards from the succeeding spot. Lifts a hand or hands from the ground upon initial charge by B1, who (a) does not enter the neutral zone or (b) enters the neutral zone but does not threaten the position of A66 or A72. RULING: In both (a) and (b), blow the whistle immediately. Team A
dead-ball foul, false start. Penalty — Five yards from the succeeding spot. [Cited by 2-18-2-d, 7-1-2-b-3-a, 7-1-5-a-2]
NOTE: Before the snap, a team B player who enters the neutral zone may threaten a maximum of three Team A linemen. If the Team B player enters the neutral zone directly toward a Team A lineman, then that Team A player and the two adjacent linemen are considered to be threatened. If the Team B player enters the neutral zone directly toward a gap between two Team A lineman, then only those two Team A players are considered to be threatened.