Visible crew/equipment: When McMurphy tries to make the "dancer" vote for the world series he dances with him through the hall. When he does that you see the shadows of the boom mike and cables on them. (00:43:50)
Visible crew/equipment: In the second basketball scene, when McMurphy shouts at Martini because he threw the ball against the fence, there's a lot of equipment visible on the left side, most prominently a big spotlight. (01:05:20)
Answer: 1) McMurphy didn't exactly "get off" by reason of insanity; he was still incarcerated for an indefinite amount of time, just in a psychiatric facility rather than a traditional prison. 2) He was originally sent to a normal prison for the statutory rape charge, but is then transferred to the mental hospital due to repeated acts of aggression that suggested some form of psychosis (or, as the doctor suspects, faking it to get out of hard labor). 3) No, it wouldn't. The insanity defense is a) very rare and b) very hard to prove, and it would be difficult to apply to rape, statutory or otherwise.