Udates and old computers

"Update today and now photoshop is not compatible with windows 8"

The last version supported for Windows 8.1 was Photoshop CC2018, you would not have been offered newer versions from the Creative Cloud app

https://helpx.adobe.com/ie/photoshop/system-requirements/earlier-versions.html

So what exact version do you have installed and what exactly is the issue you have, does the program not load, are you getting an error message

You can download at least the last version of PS, but all software companies will eventually stop supporting older operating systems. PS is one of the few software's that I use all the time, so it drives what computer I get and when I upgrade my OS. 

This is a user Forum, so you are not really addressing Adobe here, even though some Adobe employees thankfully have been dropping by.

Please read this (in particular the section titled "Supply pertinent information for more timely and effective answers”):

https://community.adobe.com/t5/using-the-community/community-how-to-guide-tips-amp-best-practices/td-p/11601738?page=1

If someone updates to a program version that doesn’t run on their OS isn’t that up to themselves? 

https://helpx.adobe.com/photoshop/system-requirements.html

https://helpx.adobe.com/photoshop/system-requirements/2020.html

You should be able to roll back to Photoshop 2020. 

https://helpx.adobe.com/download-install/using/install-previous-version.html