Since it's a manual adapter , set camera "release shutter without lens" to enable when using the adapter for the first time, or the camera will fail to recognize the lens and the shutter may not be released. (Exact naming and location of this option may change depending on camera model). 

Adapting APS-frame lens to full-frame camera may generate vignetting, which is not caused by adapters (some cameras could correct it by adjust APSC). On the other side, Adapting full-frame lens to APS-frame camera provides excellent edge-to-edge sharpness. The smaller image field helps minimize the effects of lens distortion and aberration by using the 'sweet spot' or center of the larger lens image circle. And it will magnify the focal length by 1.6 on Canon, 1.5 on Nikon and Sony, 2.0 on M4/3 camera. 

No, it's a manual adapter without electronic contacts, doesn't support autofocus/auto diaphragm/aperture control. 

Our adapters support to focus to infinity. Since it's a manual adapter, if you come with this issue, please try to set the camera as MF (manual foucus) mode, then turn the focus ring to the infinity (∞). And please try to turn back a little to achieve focus to infinity in case the infinity mark of some lenses is not accurate enough. Besides, the position of the infinity mark [∞] of the telephoto lens or super telephoto lens is shifted slightly to the positive side to enable focus adjustment even when focus shift is caused due to temperature changes. The shift range is denoted by an L-shaped line, please be sure to check the focus through the viewfinder even when you shoot at infinity.