Yes they prevent the lens melting. I have a set, and they are bright, but they don't focus the light rearward as the designer intended. I have a new set of LED bulbs on order that promise work better with the reflector.
I checked. The seats as shown are symmetrical with respect to their mounting hook. However, the left side "floor socket" on a W463 does not seem to be in the same place. You can measure for yourself if you flip up the rear bench and measure from the side to the hook.
At least you could cut your trees. I have neighbors on both sides that "love their trees". These things are basically unlit roman candles. Pines, Eucalyptus, Live Oaks, with a few Redwoods mixed in to help slow down the flame front.
There is quite a lot of nonsense in that video. Some of the biggest California fires have been in wilderness areas that have never been managed and never will be. What has changed in these areas is the climate. It doesn't take much of a temperature change to drastically change our environment. Back ...