VEVOR Red Light Therapy Device, Portable Red & Near Infrared Light Therapy for Body and Pets, Handheld Red Light Healing Device with LED Display for Muscle Pain Relief & Dogs, Cats (12*650nm + 4*808nm

It cannot be changed, the wavelength of light is fixed.

It is invisible light, that is, you can't see the light

I have used it on my cat for a throat irritation. She doesn’t tolerate it for very long because she gets antsy. I doubt it has helped since I can’t do it for too long. I believe red light therapy does help with pain and discomfort because I use it myself.

No, that can't be done.

It's CLASS 3B.