Well, as there is no communication from the computer to the projector, other than the screen-contents through the (probably) VGA cable, you can't sent commands to the projector. Unless some manufacturer has added that feature to the projector. And then it would most likely be proprietary and the software would/should be delivered with the projector. Highly unlikely you'll find this on your range of projectors.
The advice given all over the internet (as you linked and more) is to use the projector as an extended screen, Powerpoint will by default use that to display the presentation on even when PP itself is on the main screen, and once you minimize PP, or give focus to another application on the main screen, you can continue different work there while the projector is happily displaying the original content.
To switch the external monitor to be used as an extended desktop, use the <Win>-P keyboard combo, and select the desired output mode. Works with 99.99%+ of all laptops, AFAIK. Once extended you can configure the resolution for the projector using the standard Windows Screen Resolution configuration screen item, if it's not set correctly by Windows while detecting the external 'monitor'.