I've been watching college football since 1988, and I'm still confused on the rules of the "False Start."  Here is my understanding of the rule:

1. All players must be "set" before the ball is snapped, so any movement by an offensive player other than the center results in a penalty.  Set meaning: once in a stance the player cannot leave that stance.
2. The exception to #1 is that one player may be in motion, laterally or away from the line of scrimmage.

My confusion comes from when are players considered set?  Before spread offenses gained popularity and when teams used to huddle, I had no real confusion. Please address how these other examples are legal:

1. Quarterbacks can clap and motion players.
2. Quarterbacks can look to the sideline, then walk up to the line and audible.
3. Lineman can't flinch or fall backwards, yet they sometimes pivot in their stance.
4. Lineman can put their hand on the center when he's ready for the snap to occur.
5. In the OSU/MSU game, Conner Cook lost his balance (flailing arms) before the snap, but no penalty was called.

Can you guys who definitively know the rules, please explain some of my points?  Thanks!