Can anyone tell me how much stinging during laser pulse therapy for skin tightening on face?

Varies. The type and extent of discomfort associated with laser and radiofrequency therapies on the face vary by the type of modality being used. For radiofrequency type skintight such as relift by viora, the discomfort is minimal at best and it's more of a mild suction than anything else. This is generally what i would recommend for skin tightening on the face.
None to a lot! Ask for nerve blocks. If your doctor can't do this find another and it will be relatively painless. Infrared tightening can be done without anesthesia and is safer.