Illegal Shift Question

[mrm21711]

First off...Im a long time baseball guy who is a few years into football and enjoying the challenge and experience of football.

Had a situation pop up the other day regarding a shift and was looking for some clarification. In my mind, the rule and case book and the Reddings NFHS study guide are leaving me a bit confused. My questions are about the definition of an "interior lineman" and if a lineman/player puts one hand on the ground.

I am under the understanding that interior lineman can shift if they have not placed a hand on the ground (i.e. in a 3 point stance). Am I correct to think of the definition of an "interior lineman" as the two guards each next to the center or would this definition also apply to tackles and/or a tight end who is not on the end of their part of the line?

Lets say on one side of the line next to the Center is a Guard, Tackle, and a Wide Receiver who is on the line. Can that tackle and guard shift legally?

Is any player on the line who goes into a stance with one or both hands on the ground ineligible to shift and if they do, it is an illegal shift?

If I am missing anything else feel free to chime in, all help is much appreciated. Thanks!