I am trying to inset N-gon face but failing.

Create cube. Delete top and bottom faces.

Add separation with Ctrl-R so that it is not in the middle of a face:

Fill top hole with F. It will be a 5-gon. Select it and start inset

Make it smaller than the distance between center and additional separation. Dithering begin.

Is n-gon prohibited situation? How to fix out of it?

I am trying to inset N-gon face but failing.

Create cube. Delete top and bottom faces.

Add separation with Ctrl + R so that it is not in the middle of a face:

Fill top hole with F. It will be a 5-gon. Select it and start inset

Make it smaller than the distance between center and additional separation. Dithering begin.

Is n-gon prohibited situation? How to fix out of it?

I am trying to inset this big face on top but failing

This is because top face was whole and adjacent faces were not.

Is this prohibited situation? How to fix out of it?

I am trying to inset N-gon face but failing.

Create cube. Delete top and bottom faces.

Add separation with Ctrl-R so that it is not in the middle of a face:

Fill top hole with F. It will be a 5-gon. Select it and start inset

Make it smaller than the distance between center and additional separation. Dithering begin.

Is n-gon prohibited situation? How to fix out of it?