Unable to display full screen with control buttons

[Winr]

The computer recently started to display screens that are not full screen. If I do select full screen it opens without the control buttons i.e. minimize, maximize, or close. I ran SFC and DISM scans without success.
System details: Dell 32 bit desktop
Windows 10 Pro
Version 21H1
OS build 19043.1889
Installed RAM 3 GB

 

[Bighorn]

Full screen is different from Maximized, hides toolbars and the Title bar [with the 3 control buttons] so as to gain more screen 'real estate'. It usually is activated by the F11 key or on some Notebooks the Fn + F11. If the middle button has the single square on it click drag of the Title bar can move the window around, moving the mouse pointer to one side or other can resize it. Clicking that middle button Maximizes and shows 2 overlapping squares, clicking again Restores to the previous state.

Maximized

Full screen

 

[Winr]

Thanks much Big Horn for your response. Now that you have clarified the terms full screen and maximized, I want to concentrate on full screen. In the past the display used to fill the entire screen. Now it only fills a portion of the screen. I want to get to the situation where I have the 2 overlapping squares with a fullscreen. And I cannot do that now. Thanks again.

 

[Bighorn]

As far as I've seen Full Screen only works with the window/program that has the focus [is active].