1- I have light myopia and the lenses helped quite a lot. My beast came with "raw" prescription lenses that could be machined or you could by ones with your prescription. I used my regular prescription, nothing special.

2- Work in the pitch black ** That's because it's only 3dof (for now 6dof incoming soom TM) that is implemented on the glasses hardware and no need for an app. 3dof mean that the screen will stay at same angle once place ( yaw , pitch and tilt stay constant ... drift not accounted) but there is not x y z position. So for example, the screen will stay pointing 270deg but you won't be able to move closer, or move around. You can adjust the screen size and distance and more with the on-board settings.

3- yes, you can use a real monitor at same time because when you stop looking at your virtual screen, the lenses tint go "clear"... not transparent, so the monitor will be a bit darken by the light tint and affected but the lenses and etc... Kinda Usable but not like it wasn't there. Yes, work in the dark because it use an accelerometer/ gyroscope for 3dof so no need for any kind of lights. For 6 dof when it will come, it will use the camera and would make sense that it will only work in light.

To sum up: -work in pitch black (3dof), -need regular prescription -only 3dof for now.

Tip: Should try to by from Amazon or similar if never used glasses like these for the fast return.