5.1 lollipop - how do I enable 180 degree screen rotation on Moto G (3rd gen)?

how do I enable 180 degree screen rotation on Moto G (3rd gen)?

Portrait is default
Landscape rotates the screen by 90 degrees

but is there a way to enable auto rotate for 180 degrees (upside down/reverse portrait) without root access

Answer

Use Rotation - Orientation Manager (7-day trial). It allows you to set the orientation per app or globally. "Reverse Portrait" is what you're looking for in terms of 180 degree.

_{(Click image to enlarge)}

Alternatively, for my Paranoid ROM (AOSP; Android 5.1), using adb I can enter on PC:

adb shell settings put system user_rotation 2

It achieves the same goal.

On further search, I found some notable mentions: