it matters what position your in but everyone goes into play when the ball is snapped?
The holder
When the ball is snapped on the play following the penalty.
then you can't put it back on.
Encroachment is when a defensive player makes contact with an offensive player at the line of scrimmage prior to the ball being snapped. Unabated to the quarterback is when a defensive player charges across the line and is on his way to the quarterback before the ball is snapped.
Yes. As long as there is one second left when the ball is snapped, the play counts.
It's called a false start.
Quarterback and running back
offsides. penialzed 5 yards
Yes, as long as they dont cross over the neutral zone
Yes, because the play starts as soon as the ball is snapped.
It's "green" 18, not "3" 18. It's the start of his snap count. The ball is then snapped on a one or two count following. He conditions the defense to assume that the ball will be snapped on one or two. He then sometimes shouts an exaggerated hut-hut following green-18 but the ball is not snapped (called a "hard count") to try to draw the defense offside. The hard count only works if the quarterback has been consistent in his pattern up to that point.
The ball must be placed on the line of scrimage before snapped. Assuming you are referring to a place kick or a punt, there is no rule dictating where the ball must be snapped to. Seven yards is standard as it should give the snapper, holder and kicker sufficient time to perform the kick.