proof of concept, though. you can fill a tank from the bottom, as long as whatever is draining is above the top of the tank.
Yes, it will work. (As you just explained)
This is for the same reason that a pump that is 150' deep in a well doesn't have to pump 150' of head pressure. Only the difference between the water at the surface and the height where it exits the pipe.
Or, hold your garden hose ends up off the ground. Pour water in one end (slightly higher), it will flow through the hose and rise back up and flow out the other end.
Clear as mud??