6) Neward Industries makes a bottle attachment lid for their adapter plates to hold the bottle upside down on the top of the master cylinder while you bleed the brakes, without running out of fluid. It works just like a bird water feeder. As the level goes down, more fluid flows in.
8) The rubber seal in the lids of all American master cylinders keep the fluid from flowing back into master cylinders that are mounted lower then the wheel cylinders. Bad master cylinder lid seals, or vented caps, will allow fluid to flow back into a low-mounted master cylinder.