> Is backwards compat a thing on osx? It really depends. I managed to get a universal intel 32/64-bit app compiled on OS X 10.5 run on Catalina, which is 10.15

> Is backwards compat a thing on osx? It really depends. I managed to get a universal intel 32/64-bit app compiled on OS X 10.5 run on Catalina, which is 10.15. But it was a very unremarkable app. Just a simple NSWindow and label. Nonetheless demonstrates you can technically have some backwards compatibility. At one point in time (say 2004), you would've been able to launch Classic environment on a PowerMac G5 and emulate 68k software in Classic, all the while enjoying OS X software natively. That should span some decades worth of Macintosh software, but of course this era is simply gone now.