How to use Fixed Background

Questions & Problems
#1

How does fixed background work?
I was trying to use it many times, and it doesn’t look to work as described in docs.

How I understand, it should kind of create temporary layer and let me do quick paint over my image without changing it, so I could eventually erase changes and leave fixed background unscratched, but it just doesn’t seem to do anything when I activate fixed background option.

#2

On layer 1 draw your background. Then use the fix image icon when your background is complete. Now when you erase you will have your background.I hope this helps.

#3

This doesn’t seem to work I am still erasing both fixed background and new overpaint