I take it this device allows the camera to use it's a/focus circuit, and when installed and working it gives the beep / green light to confirm focus.
Does it let the camera respond when you change the f stop? You mentioned the camera displays f2.0, if you manually change the aperture on the camera, does the displayed figure change?
Would this separate the 'chip's from the trees' if the displayed figure matched the scopes f/l.
Nope..
You can not change the f-number because this, displayed, 2.0 is reading from ROM (Read-Only-Memory), just to fool camera that the manual lens is attached.
However, camera will adjust the exposure time (in AV) as you manually change the f_stop of the lens, because the amount of light is changing.