Rosetta 2 is the newest version. The universal apps are just an export in XCode from what the presentation made it seem like. Developers exclaiming it took 10 minutes to do the universal app build.
Universal apps have existed since the transition from PowerPC. For most apps it's simply recompiling in Xcode and it creates a fat binary with both architectures.
Any apps that rely on specific intel libraries will have a bit more work to do.
No, "Universal" apps in this context means these apps can run in Mac OS, either on an Intel Mac or on an Apple Silicon (ARM) Mac. Nothing at all to do with iOS, iPadOS, Windows or Linux.
Isn't that misleading marketing? I know that companies can call their new efforts whatever they want, but if someone sells a "Universal keyboard" that only works with Windows, isn't that just straight up misleading marketing?
The only thing that comes close to being "universal apps" would be applications that run in a browser.