This might be a silly question, but...
 

In Texas we play with NCAA rules, in We are playing out of state and want to know the difference between the NCAA rules and fed rules when it comes to cut blocking. Thanks

NFHS does not allow any blocks below the waist except in a very limited area for a very limited time.
First, there is a free blocking zone, an 8 yd by 6 yd rectangle centered on the ball at the time of snap.
Second, the blocker must be on the line and in the fbz at time of snap.
Third, the blockee must be on the line and in the fbz at time of snap.
Fourth, the block must occur within the fbz.
And Fifth, the ball must have never left the fbz before the block.

So if the snap is to the shotgun, can a cut block still take place by a OT on a DE that are both on the LOS that occurs when the ball is snapped?

According the the NFHS case book (similar to the NCAA Interpretations section), if the block is immediate with the snap, it is legal.
However, you better check that with the officials at your game. Some areas, like mine, have ruled the ball is out before the block can possibly be made and is therefor illegal.