Possibly but I would recommend contacting the manufacture.
Yes these grips will work with an ambi-safety selector.
Yes it will.
Yes, the same mounting screw will work.
Yes, this grip will ft the FN-15 Guardian rifle.
Yes it will fit with no gaps if installed correctly.
Yes, this grip will fit on and work with the VR80 shotgun. Please know that you will need to replace the OEM buttstock as well with one that fits the Commercial sized buffer tube.