For camera with telephoto zoom lens, you need to buy a tripod mount ring additionally or telephoto lens bracket for better balance) 

That may be caused by the fact that the lens weight is much bigger than camera, If used your telephoto lens with our adapter ring, we suggest to use with a lens bracket and better to shoot on a tripod to increase its stability. 

The longer Flange distance lens to the shorter Flange distance camera, then could use the infinity focus.
but if the shorter Flange distance lens to longer Flange distance camera, then could not use the infinity focus, you can focus on a limited distance.
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, Be sure to check the focus through the viewfinder even when you shoot at infinity. 

No 

To hold telephoto lens, it is recommended to use a tripod mount ring additionally for better balance. Meanwhile, it is better to hang some heavy thing to the hook to lower the center of gravity on this tripod to make it more sturdy and less prone to vibrations.