Unable to change CoreWindow resolution after initialization

So my Xbox does not support 1280x720 resolution…but I’m able to set it on initialization…by creating a widow with the specified width and height.

After selecting the store while the game is running, Upon returning the resolution changes to the desktop size 1920x1080.

How can I change it back to 1280x720?

I tried all methods I could think of…

thank you.