I’ve done hardly any game development in my life (making a simple Gamemaker game at high-school in 2016 or 17, & making a box fall in Unity a couple years back; so you can call me a complete noob. But I was just wondering: If I for whatever reason wanted to make my game work natively on a Bunch of different Windows versions, like 95, 98, 98SE, 2000, ME, XP, Vista, 7, 8, 8.1, 10 & 11; would that be possible without making separate versions of the game for different Windows versions? It sounds like a cool project for doing just for the fun of it, for learning about the different OS versions once I already have more experience with development on modern Windows. What if I made the game on Godot game engine? Can Godot games even run on such old operating systems? I heard that Windows 2000 and above are NT based, and major Windows versions prior to that ran on something else: would this greatly affect the development process at all?
Clarification: Sorry, but I should have clarified that my development platform is Linux, and would be porting to Windows, which obviously should change the answer to my question drastically; I have no idea why I worded things to sound like I would develop the game on Windows first and foremost; but that was my mistake.
I think using OpenGL will be even harder than DX8. Your point with the documentation is spot on: it will be hard to come by. As for TLS/SSL third party libs: I had the fun opportunity to implement/maintain the backwards compatibility for a piece of software for Win XP/Server 2003 ~3 years ago. We had to jump some hoops with a custom compilation of OpenSSL to get the parts of TLS 1.2 we needed in Windows 10. I can say with confidence, that that route is a dead end for even older Windows versions.