1. If you're in VNAVSPEED it will not make speed/altitude contraints unless it RECAPTURES VNAVPATH. Your question stated "in VNAVSPEED" so the answer is no.
He didn't ask about speed/altitude constraints on the LEGS page, he was asking about the speed transition at 10 000', programmed through the VNAV DESC page . The aircraft WILL make that transition in VNAV SPEED, provided the speed window is closed.
3. Yes, as long as it stays in VNAVPATH. Change the speed in the FMC, understand why, and what, changes occurred to the descent profile, and if it transitions to VNAVSPEED you should be able to figure out how to regain VNAVPATH(piloting 101)
Mis-read his question, I thought he said speed window OPEN, but, yes with it closed you are correct.