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after update last night no mac apps ( safari, numbers, etc) only firefox, activity monitor etc on right side of dock doc will open. Can not open apps from finder either.
reinstalled os Catalina 10.15.3 with same result
10.15.3 is the latest..
https://support.apple.com/kb/DL2030?viewlocale=en_US&locale=en_US
Do you have a Time Machine backup to Restore to/from?
https://support.apple.com/guide/mac-help/revert-to-a-previous-macos-version-mh15216/mac
Reinstall the OS...
1. Start up from macOS Recovery
To start up from macOS Recovery, turn on your Mac and immediately press and hold one of the following combinations on your keyboard. Command-R is generally recommended, especially if you never installed macOS Sierra 10.12.4 or later… https://support.apple.com/en-us/HT204904#notupdated
Command (⌘)-R
Install the latest macOS that was installed on your Mac.
Option-⌘-R
Upgrade to the latest macOS compatible with your Mac.
Shift-Option-⌘-R
Install the macOS that came with your Mac, or the closest version still available.
2. Decide whether to erase (format) your disk
If you need to erase your disk before installing macOS, select Disk Utility from the Utilities window, then click Continue. You probably don't need to erase, unless you're selling or giving away your Mac or have an issue that requires you to erase. Learn more about when and how to erase.
3. Install macOS
After starting up from macOS Recovery, follow these steps to install macOS:
1 Choose Reinstall macOS (or Reinstall OS X) from the Utilities window.
2 Click Continue, then follow the onscreen instructions to choose your disk and begin installation.
3 If the installer asks to unlock your disk, enter the password you use to log in to your Mac. If it doesn't see your disk, or it says that it can't install on your computer or volume, you might need to erase your disk.
1 Please allow installation to complete without putting your Mac to sleep or closing its lid. During installation, your Mac might restart and show a progress bar several times, and the screen might be empty for minutes at a time.
If your Mac restarts to a setup assistant, but you're selling or giving it away, press Command-Q to quit the assistant without completing setup. Then click Shut Down. When the new owner starts up the Mac, they can use their own information to complete setup.

If you never installed macOS Sierra 10.12.4
If macOS Sierra 10.12.4 or later was never installed on your Mac, macOS Recovery works differently:
• Command-R is still the recommended way to start up from macOS Recovery. This combination makes sure that the installation isn't associated with your Apple ID, which is important if you're selling or giving away your Mac.
• Option-Command-R installs the macOS that came with your Mac, or the closest version still available.
• Shift-Option-Command-R isn't available.
https://support.apple.com/en-us/HT204904
I already did reinstall the OS and still no improvement, I really would like to install the previous os version The latest is Catalina 10.15.2 which automatically installed last night, which is when the problem started
tried installing back to original OS but Lion would not recognize SSD drive, all other options go right to Catalina and back to where I started. The only thing that I can start is Firefox and sketchup
Well, no Late 2012 Mac originally came with Lion so you can understand the confusion.
FWIW, I have "Show recent applications in Dock" disabled so I have no Apps on the right side of the Dock.
You could try deleting ~/Library/Preferences/com.apple.dock.plist then run "killall Dock" in the Terminal. You would have to re-add any apps you added to the Dock.
Safe Boot from the HD, (holding Shift key down at startup), does the problem occur in Safe Mode?
If no help then Re-install the OS.
No time machine because its not used much and every file that is used is backed up to icloud. But I just want to get it operable, right now it is a doorstop and unusable
Lion? How old is your Mac? You can't install Catalina on a Mac older than 2012.
late 2012, Catalina was installed on there up until the last automatic update without issues
after update last night no mac apps ( safari, numbers, etc) only firefox, activity monitor etc on right side of dock doc will open
