First, K&F Concept ND2-ND400 lens filter allows changing shutter speed based on the effect you want with the best sensibility and the same aperture. Second, K&F Concept ND2-ND400 lens filter allows creating a blurred background with a large aperture while the shutter speed remains the same. Third, K&F Concept ND2-ND400 lens filter is designed to prevent overexposure and maintain image purity and quality at the same time. *Like a zoom lens, the variable nd filters are suitable for multiple shooting situations. If you're looking for perfect image quality, a fixed ND filter is recommended. 

Yes 

This issue could be improved according to following suggestions:

1. Q1: Camera shutter does not release when lens is attached
   A：The lens is fully manual and does not have electrical contacts. Please switch your camera to "M" (manual) mode
2. Q2: Images are too dark
   A：Lower the f-stop on the lens, and/or lower shutter speed, and/or raise ISO settings on camera
3. Q3: Images are too bright
   A：Raise the f-stop on the lens, and/or raise shutter speed, and/or raise ISO settings on camera
4. Q4: Images are not coming out in focus
   A：a) Adjust the focusing distance on the lens to the correct distance.
   b) In certain photographic situations, you may find it easier to focus at f/5.6-8 rather than f/3.5

 

1. If there is ever any more than a slight amount of rotational play, you may want to try tightening the lens mount adapter so it will hold the lens tighter to the mount. There are 3 flanges in the middle of the adapter (what the lens locks onto) that are split open slightly, this gap is what gives the tension that holds the lens tight to the body. Over time and with use these gaps decrease in size, no longer pulling the lens tight to the adapter, which allows the lens to move inside the mount more than it should.
2. To tighten the fit, get a slim metal object (a #1.5 or #2.0 small flat eyeglass screwdriver is ideal) and insert it into the slit to open it up just a little bit (see images below, make sure to do it to all 3 evenly). The more you open the gap, the tighter the lens will be to the adapter; too much and the lens will have a hard time mounting so make sure to do it just a little bit at a time to all 3 flanges evenly, it doesn’t take much at all to get a tight fit.Note: please do not use too much strength, or the shrapnel will be damaged.

 

I don't think you need any. There is no glass.