What keystroke combination put Mac’s display to sleep? When I hold down the Option and Command keys, and then tap the key at the upper right on my Mac’s Apple OEM keyboard, Nothing happens on the K...

Hold Option–Command–Power button* or Option–Command–Media Eject: Put your Mac to sleep.

Control–Shift–Power button* or Control–Shift–Media Eject: Put your displays to sleep.

 

You can use VIA to remap a key to the power button or media eject and try the key combinations mentioned above. Click on the link to learn more about how to use VIA.