I have the following question:

1. Is a flashing kickout at the bottom edge of the roof/wall joint used to help keep water from getting behind the stucco or siding?

Not really a plumbing question but here goes. A flashing kickout is where a vertical wall meets a lower roof line. The kick out is stepped on top of itself as you go up toward the peak of the roof line. So yes, it does keep water from getting behind the siding.