OK everybody here is another one.......

1st and 10 for A at the B 41 yd. line. A comes to the line of scrimmage and A5, wearing No. 23, assumes a 3 pt. stance in a gap between the tackle and the end, with his helmet penetrating the plane created by the waist of the tackle. At the snap (a) A5 fires out and blocks tackle B9 below the waist, while the ball is still in the FBZ and B9 was on the line at the snap, or (b) A5 is in motion parallel to the line of scrimmage and 1 yd. behind it, or (c) A5 goes downfield and catches a forward pass and is downed at the B 27. Is there a foul? If so, what is it and how is it enforced?

In (a), team A still needs 5 lineman numbered between 50-79 to avoid a foul and A5 needs to be in the zone, but if they do, we are fine. If not IFormation, live ball foul, enforce 5 yards from PS.

In (b), if he started on the LOS, then he must be 5 yards or more behind the LOS at the snap if he did not establish himself as a back... - if not illegal motion at the snap, live ball foul, enforce 5 yards from PS

In (c), If he was covered up, since he is an ineligible receiver who caught a legal forward pass which crossed the LOS, we have OPI - 15 yards from PS and LOD

In (a) you say that his helmet penetrates the plane of the
tackle's waist line, but nothing was said about the waist line
of the snapper. If his helmet penetrates the plane of the
snapper's waist line, then he is on the line. If it does
not penetrate the plane of the snapper's waist line... he is
NOT on the line, if that is so then he must have his hands
in position to receive the ball, if not ... illegal formation.
7.2.3 which references 2.30.3

If the back is not legally on the line as described, then
you also have an illegal block below the waist.

(b) illegal motion 7.2.7 if he is in no man's land... not
legally a back and not legally on the line when set.

(c) I am assuming that A5 was not on the line, and that
A5 was not legally in the backfield... therefore you
start with the illegal foramtion, then when A5 touches
the pass you have offensive pass interference because
A5 is not eligible and has touched it beyond the line of
scrimmage.

7.2.3 and 7.5.10

In B, can he raise up out of the three point stance? I thought in Fed ball once you're in a three point stance on the line of scrimmage, you cannot move, even if you are an end. Not like in NFL where you see TE doing it all the time.

Depends if he is really on the line or not, and that is only true for interior lineman. Since the question said he
was in a gap, then if on the line then you are correct he
cannot move. TEs in federation ball can rise up and move,
as long as they don't simulate action at the snap and then
reset legally ( a shift ).
ref. 7.1.7c.

If he was in "no man's land", not a back and not on the line, then he can go in motion but must comply with rule 7.2.7.

The part about his helmet breaking the plane of the tackle's
waistline puts him in the not a back catagory. If his helmet also breaks the plane of the snapper's waistline then he is a lineman.