os Catalina update to newer os

FrankS74NZ wrote:

... how do I revert back to Catalina assuming this is possible

The first thing you do is make sure your computer is backed up with Time Machine. You can use that to restore your Mac if you have trouble.

Back up your Mac with Time Machine - Apple Support

And/or you create a bootable usb installer now, while Catalina is healthy.

Create a bootable installer - Apple Support

Unfortunately there is no easy way to return to Catalina once updated. You would need to erase the computer and install Catalina from scratch, then install your apps to go back.

I would verify with the app developers if they have versions compatible with a more current macOS version before taking the plunge.

The other option is to install the updated macOS version on a different drive or volume, even an external one, to avoid affecting your current Catalina installation. That way, all you would need to do to return to Catalina, is to select your internal drive during boot up or just disconnect the external one.

You can test your apps from the external drive and see if they work, before committing to upgrading your current Catalina installation.

https://www.macworld.com/article/672585/how-to-install-macos-on-an-external-drive.html

It is not easy to go back. You should make a bootable usb drive and boot from that and reinstall Catalina.

But.. there can be issues with reaching the recovery servers while installing older macOS versions

What I would do is to check the system requirements of your programs if they support the latest macOS

You have an iMac that is perfectly capable of running the newest macOS 14 Sonoma, but you're willing to continue using a macOS version that is already four generations old? Catalina is already showing its age. A macOS upgrade has the potential to prolong the usable life of that iMac Pro by years!

I agree with Phil0124's suggestion to check with the developers of your apps and see if they support the latest operating systems.

And I do hope you are backing up with Time Machine. Catalina is, I think, the last OS that can be restored directly from a TM backup set. That makes recovery pretty easy, actually, contrary to what you imagine.

It's your iMac so the choice is your, of course, my friend. But I'd hate to see you become one of the many who wait to upgrade until it's too late and much more difficult.