Hi, Notice： If your camera indicated "lens is not properly installed", please modify the camera menu settings. Usually called the "release the shutter the lens is not installed", you can modify the settings to be allowed. Specifically refer to the camera manual When using the adapter ring for the first time, please say that the "No lens release shutter" option in the body menu is turned on, otherwise the lens will not be recognized and the shutter will not be used to take pictures. 

Hi,this is not compatible. 

I would think that it would be no problem, as long as it has a 1/4-20 threaded mount on the camera. I might suggest looking for a video tripod, though, over one designed primarily for stills cameras. A video tripod will give you smoother control over panning and tilting maneuvers. 

Absolutely. 

Hello the filter size is 58mm, so as long as your lens size i s58mm, the filter can work with your Canon EOS 20D