This is more a question of your glasses and not the lamp. She produces light. If your glasses have an anti-reflective coating, the lamp will not be reflected in the glasses, depending on the level of anti-reflective coating. (It should be noted here that the anti-reflective levels trigger different colors, level 2 triggers a blue tone in the glasses, level 3, which is the most recommended for working on the PC, triggers a green tone. This goes badly with a green screen , if the plan was to connect this to it) 

Hi, I'm pretty sure the dimensions of the S21 you state are no bigger than my iPhone 13 Pro Max? Given this being correct, it will fit and operate okay. As a footnote, the X2 is excellent and works terrifically well... 

Yes, it can run indefinitely after being plugged in. 

Of course you can, it is highly absorbent and you can stick it to any smooth place such as walls, mirrors, computers, iPads, desktops etc. 

I am pretty sure any smart phone will work with this monocular. We have not yet gone SMART but intend to. Good luck if you buy , it’s great