1) My lcd mentioned in the specification as 55-75hz. in the monitor setting it is allowing me to set the refresh rate to 75hz while the hide unsupported refresh rate is ticked. So is it ok to run the display on 75hz? WIll it damage the panel in long run?
2) If i set display to 75hz. Will my adaptive v sync automatically start working on 75hz or will be locked to 60hz as before? I play very old games so i need adaptive v sync.
75hz is within the specification of the monitor and as such you will be fine running at 75hz. I personally have never known a monitor to be damaged by an incorrect refresh rate setting. The usual thing is that the monitor flags a message saying that the refresh rate is out of range.
V-Sync makes the GPU wait for the monitor to signal that it is ready to be feed the next frame. This is the refresh rate.
So if you are set at 75hz then it will cap at 75FPS.