It is generally not a good idea to do that because it would allow the batteries to short through the walls of the light. However if you have something else to recover it with it should be okay.
Ed: The Hi-Max has two layers, white under, clear over. You can remove the outer clear layer but be warned that the under layer is somewhat brittle. Just treat the batteries carefully and inspect them for nicks in the future.
As mentioned before, the HiMax cells are double wrapped. The white layer is pretty much like the one from the old white-blue Solarforce cells. Its OK but, as said, brittle.
Not a problem for the most part. However, unless you get a special charge for them (or have a hobby charger) then they are not going to reach that voltage.
This are only 4% more and I don’t think, that this will harmful (in a single 18650 flashlight). But I would not try to use 2-3 of them in a flashlight in serial.
This depends on the actual cell/battery, in my battery review I do test cells/batteries that need higher voltage, both at the high voltage and at 4.2 volt. You are not required to use the higher voltage, but will get less capacity when using the 4.2 volt on a 4.3 or 4.35 volt cell. To see how much you loose, check my reviews.
My Hi-Max 18650 needs to be rotated until the ‘sweet spot’ is found to fit in the UF T50 and then it slides right in, albeit quite snugly. It’s a slight nuisance but manageable. However, if there is going to be trouble with them fitting at all in some lights then it’s a pretty big issue, imo.
Try rotating it as you let gravity (and maybe just a little bit pressure) force it down. It’s the positive end (PCB) that hangs up so once you get past that there shouldn’t be any more issue. That’s the case with mine anyway.