Yes, it can connect with most brands and models of helmet headsets via Bluetooth. 

Connect to your phone and activate the voice assistant as usual. 

Yes, they are compatible with iPhones, Androids, and other Bluetooth-enabled devices. 

No, you can't sync two of these to use. 

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.