It all depends on what defense you are running, and what play is being called by the Defense.
In the 3-4 defense (or any formation starting with "3" - as the first number is the number of defensive lineman on the line of scrimmage), the Nose Guard/Tackle would line up right over the ball and his first job would be to take on the center.
In a 4-3 - (with 4 defensive linemen on the line of scrimmage) - you aren't necessarily playing the center man to man. Unless you are running a "stunt" - the 4-3 usually carries the notion that the 2 inside D Linemen (on either side of the Center) are going to be taking on the two Guards on either side of the Center - engaging them or passing by them with a "move".
A Nose Guard/Nose Tackle's job most times is to occupy the Center and then willingly absorb one or two of the Guards at the same time, as to leave no O Linemen to pick up his Linebackers - leaving a possible free-ride to the QB, or filling a "gap" that the ball would be run through by one of the Backs.
The above is "typical", but NOT the only options for defensive formations.
It really depends on the play call.
it is not legal to drop kick beyond the line of scrimmage. all you can do beyond the line of scrimmage is pitch the ball backwards.
there must be 7 men on the line of scrimmage, no more no less
on tv, the line of scrimmage is usually blue and the first down line is usually yellow.
Line of scrimmage.
the line of scrimmage
On the offensive side, nobody has to be in a down position on the line of scrimmage, but there must be six men on the line. The defense does not have any regulations as to where they must line up on the line of scrimmage.
The line of scrimmage.
In the NFL, there is no such thing as pass interference (PI) on forward passes that do not go past the line scrimmage but I recently watched a college football game in which a PI was called on a forward that never reached the line of scrimmage even though I always believed that there is no such thing as PI if such pass was in the backfield (behind the line of scrimmage). So I am not clear on the rule concerning passes that do not cross the line of scrimmage, in college football.
The offense is allowed up to ten players on the line of scrimmage, need one to receive the ball from the center. But the offensive is required to have a minimum of seven players on the line of scrimmage. Defensively all eleven can play on the line of scrimmage.
10 yards from the spot of the foul. So if the hold occurred 5 yards behind the line of scrimmage, then the penalty would be a 15 yard penalty from the previous line of scrimmage. The down would be replayed.
Yes
yes