So long as it has a usb port there is no reason you could not. That being said, I have never directly powered any device from mine. I use it to charge my power banks and then use those to power other devices. Loss of a power bank because of spiked or fluctuating power (in and out of shadows, fast moving and intermittent cloud cover) may cause damage to devices that are directly connected. But, a power bank is a heck of a lot cheaper to replace. 

Yes, the height can be adjusted up or down by turning the adjustment knob. 

You don't have to collect the bracket. You can buy them directly. The packaging now contains the clip. If you encounter any problems during use or you are missing any accessories, please contact our after-sales staff. We will reply your problem as soon as possible and solve it. 

It does not come with a stand, just a background cloth and 4 spring clips. 

Yes you can, I just tested this by screwing on a 82mm polarizer filter. But keep in mind: 1) This can easily cause vignetting with wide angle lenses; 2) colour shifts because of camera sensor reciprocity failure as well as any colour casts inherent to the second filter. 3) Slight resolution and contrast losses.