Yes, the light is adjustable from off to full light, you can turn it off when the environment is bright enough. 

It can stack 2 square mirrors, and the size of the square mirror is 4*5.65 inches. 

you need to disconnect from Carplay first! 2. Then connect to the WiFi of the device, and then use the Mirror Link function. 

Yes, the lights keep time to the beat and there are different settings to allow for different light patterns.  

No. I bought it based on the claim that it would support the weight, but it doesn't. However, i have found that if I don't try to use the cantilevered function, but just use the height of the combined tripod and arm (straight up) and the ball joint holding the binoculars, I have more than enough height to see anything up to about 75 degrees comfortably. In the video, the eyepieces are at 6', and there is easily another foot of extension available.