Since lightsabers are made out of light, and all other laser based weapons, can't it be reflected by a mirror or something reflective?
No, it shouldn't be possible. The problem is that lightsabers aren't actually lasers (if they were, they wouldn't stop after 1-2m length, they'd go on until they hit something). They're some form of magnetic plasma bottle. The defences against them are magnetic or heat resistance (shields, dense metals, etc.), not reflection.
A surface which reflected charged particles would help, but the heat transfer would probably still melt it rapidly. (Lightsabers don't have much trouble with blast doors, for example, even shiny ones.)
(Even against laser weaponry, a mirror would be of limited value. The surface polish helps at first, but a sufficiently energetic pulsed laser will rapidly blow that shiny surface apart.)
Yes. The way I understand them is based on a bunch of books I purchased as a kid, so I am unsure how canonical it would be, but I think it would work. As I understand it, the lightsaber is not plasma, as some claim (it is clearly actually light), and works by the photoelectric effect, ionising a surface to the point where it is destroyed by the repulsive force of the bits ionised very strongly by virtue of the blade. By this logic, perfect mirrors which reflected all photons would block a lightsabre, and it would refract, and do everything else light does. It would also go through glass.