*IF* they want the "enhanced" seal. I remember Sony stating that they won't give you an enhanced label if you run at variable resolutions. I also remember them saying you can't add the enhanced label to your game if it's only a more stable framerate. You also need to increase maximum resolution to be able to use the enhanced label.
No, developers have to support the PS5 Pro, that much is true. Which means their game has to be PS5 Pro Certified, not enhanced. So, all games released after September 15th need to be certified to work on the PS5 Pro. Enhancements are optional.
Yes...
Yes, the mandate was only for games to be able to support the Pro. Enhancements are different.
" Sony will use a new “PS5 Pro Enhanced” label to tell players which games take advantage of the console’s new abilities, according to documents seen by InsiderGaming yesterday. The outlet writes that to get the label, a game would have to offer a PS5 Pro graphics mode, which includes PSSR for 4K upscaling, constant 60fps framerate, and added or improved ray-tracing. It would reportedly also indicate higher resolution for both fixed and variable refresh rate games. "