5 players must be on the line of scrimmage?

Answer 1

False.

This question is not asked very well as it only applies to the offense. The offense must have at least 7 players on the line of scrimmage. These can include receivers. It does not mean that the offense must have 7 linemen. Offensive players not on the line of scrimmage must be at least one yard back. The defense, on the other hand, is not required to have any players on the line of scrimmage.

Answer 2

20, I believe

Only 7 offensive players must be on the line. The defense can line up anywhere.