2. The grease is there to keep the springs from rusting. The grease holds onto the springs better than oil. Oil has a tendency to dry up and leave the springs exposed to the elements which will cause them to rust. As long as the springs are wet with oil, it will work.
4. AM/MM sear is a flat sear. The RT sear has a brass bushing attached on each side of the sear. They fit different rails and use different sear pins due to those differences. The shape of the sear looking from the side is identical for both.
6. Definitely use a level 7 bolt with a pump mag. The level 10 bolt will leak all of the residual air out of the chamber after a shot unless the bolt is cocked immediately. This makes a pump very inefficient with a level 10 bolt. Just swap all powertube parts from level 10 parts to level 7 parts.
7. The stars represented free warranty service. The valves were identical.
Except for the Automag in front, its usually the man behind the equipment that counts.