In a closed loop system the gain without the feed back loop being closed is called open loop gain!!!

e.g if forward gain is "A" and feed back factor is "B"

then open loop gain is "AB"

and closed loop gain will be [A/(A+B)]

Feedback oscillators have a closed loop gain of

Distortion is estimated as closed loop gain divided by open loop gain. If the open loop gain approaches infinity, distortion approaches zero.

no.

A: DEFINITELY NOT Open loop is defined as no feedback. any kind of negative feedback will reduce the gain