Apple announced M4 chip in Apple's Let Loose event alongside new iPad Pros on May 7, 2024.
As of May 7, 2024, the chip is used only in iPad Pro.
Apple released M3 upgrade for MacBook Air lineup in March 2024.
Resolves to the year in which Apple announces upgrade for any MacBook Air varient to the newer M4 chip.
If M4 is skipped altogether, the options resolves to No.
In fact, many such upgrades severely overload the Macbook and it crashes quite often. After installing such an upgrade, I encountered that different vertical and horizontal lines started to appear on the screen. I barely got rid of them and that only because I read https://setapp.com/how-to/fix-lines-on-mac-screen detailed and step-by-step manual, and so I really did not know what to do. So you can read it too, I hope it was useful.