Your instincts are correct.
Read Rule 2 - definitions. Don't have it handy, but a false start is defined as action that simulates action at the snap. Players don't normally "not get set" when the ball is snapped - so it's an illegal shift.
Same with going into a three-point stance at the time the ball is snapped. Players don't normally go into a three point stance when the ball is snapped, so it is illegal motion.
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