Old Photoshop cs5 won't open due to upgrade to Catalina

[SueP]

My Macbook Pro kept asking me to update so I did; BIG mistake!  My Photoshop CS5 is no longer supported on the new version because it's too old!   I can't figure out how to uninstall Catalina.  I tried "In the Finder, launch System Preferences and navigate to Security & Privacy > Privacy tab > Full Disk Access. Click the lock icon in the lower left, enter your admin username & password. Click the + icon and add Photoshop to grant access to your hard disk." but Photoshop is crossed out so it won't open.

Suggestions?  Not sure how to uninstall Catalina and install Mojave or another version again.

Thank you!
Sue

[Brian]

I’m not going to sugar-coat this...

You are fucked. 

Upgrading to Catalina is a one-way proposition. The only way to downgrade is if you either have a Time Machine Backup with the older OS and format your HD / perform a restore or have created a Thumbdrive with a older OS and then format the HD and reinstall everything.

Either way, you will need to format your HD and then deal with the issues that process creates.

Other option: Photoshop CC is in your immediate future. There are absolutely no work-arounds to get CS5/CS6 working with Catalina. The programming language that was used to code CS5 flat out will not work with Catalina. Heck, even PS CC 2015 & 2017 don’t work. Only PS CC 2019 and 2020 work with Catalina.

[Brian]

Welp, full disclosure...

I had to upgrade to Catalina yesterday to fix my iPhone 6s, which got corrupted during the latest update. So now I'm stuck with Catalina as well. The good news is, the world did not end. The latest version of PS CC seems to have the majority of bugs worked out, so if you do take the plunge and get PS CC, things should work out for you.