2- The screws for VESA provided in the case of rounded bottom so requiring to use the struts are too long. Envisaged in this case a ruler and a hacksaw to determine the length screws and adjust according to your screens. VESA holes are blind, must after tightening the screw penetrates about 5 mm and do not go to "hole".
3- The hex key that allows the tightening is standard. In case the arms are folded sharply (long side to a smaller screen as a 15 or 17 ") can be constrained to perform position (case of height adjustment) the clamping screw need loosen to adjust the height. In this case a reference to shortcut key allows not having to unfold the support arm and thus set it again.
4- The brake setting different useful joints positioning is done by tightening more or less strong six socket head screws. This is the only tricky part is very sensitive. I do not recommend too block, even after adjustment, indeed impact or unusual support (it misses, we accidentally pressed), it is better to deregulate the position (sliding) than risk forcing the structure. We must find the right setting. Here if the builder had used thread screw, precision would have been improved (I think the builder thought it was blocking position after adjustment, but we must be able to adjust sufficiently to dampen the display in position). Someone who knows tighten mounting find the right setting in two or three tries, the gap between too open or blocked is only a few degrees.