I cant get any apps to open anymore, how do I fix it?
That previous Q&amp;A should be flagged, I guess, to indicate that it's no longer a good idea. Apps are now digitally signed and notarized, and I'm guessing that editing the .plist invalidated the signature, so Gatekeeper (a macOS feature) won't let them launch anymore.
Have you rebooted the Mac? That might help. I would delete all of the apps that you modified, reboot the Mac, and try reinstalling one of them.
Then I would download and install &quot;ArchiChect&quot; from The Eclectic Light Company. Howard Oakley, who runs the site, is both knowledgeable and trustworthy.
Drag the app that won't launch to the ArchiChect app window, and see what it reports.
It's possible that you may be able to get the apps to launch by reinstalling them and then manually removing the quarantine flag. However, you should know that doing so will bypass the security features of macOS, which obviously puts you at some risk if these apps have been tampered with.
Assuming that you are downloading trustworthy apps from trustworthy developers (and not, say, &quot;pirated&quot; or &quot;cracked&quot; versions from somewhere) there probably is not too much risk, but you should be aware of it nevertheless.
To remove the quarantine flag, enter this command in a Terminal.app window:
xattr -r -d com.apple.quarantine 

Make sure there is a space after the word 'quarantine'.
Then drag the app that won't launch to the Terminal window, so you end up with something that looks like this:
xattr -r -d com.apple.quarantine /Applications/Carbon\ Copy\ Cloner.app

(I just randomly picked an app with a space in a filename to use as an example.)
If you get a message about 'Permission Denied' try the same command prefacted with sudo and then be ready to enter your login password (i.e. the password you use to log in to your Mac):
sudo xattr -r -d com.apple.quarantine /Applications/Carbon\ Copy\ Cloner.app