The incomplete part in your middle picture is the knocker. The parts missing in your knocker are the coil and plunger. Coil should be #AK-27-1300. Not sure of the plunger, but both can be ordered from PBR.

Screen Shot 2021-12-06 at 4.55.10 AM (resized).png

Maybe. As jrpinball said, "every case is different."

I have used windex and alcohol. On some reels it works fine. Careful, it may remove the paint on yours.
I have used mild soap and water. On some reels it works fine. No guarantees it will work on yours.

All depends on the paints used during production and the environment your reels resided in. A little missing paint can be repaired with a steady hand and a Sharpie (again, as jrpinball stated).