About 2nd. Does 16 have any locks to flaperons stay in place? You're right about that, they are in up position during maintenance as shown in video below
But still, i think that it is strange to keep fluid pressurized by locking isolation valves because it just increases wear of movable parts of valves and e.t.c.
Thank you for interest to this theme. One day we'll see this machine to be the best simulation of Block 50 M4.1+ in our time(Or maybe not in our...).