Can You Reinstall iOS 13?

Double-check this by clicking on the Apple logo at the top-left, then going to System Preferences > Software Update. Now you are back on iOS 13, with all of your apps working again.

Can you go back to iOS 13 from 14?

You simply can’t downgrade from iOS 14 to iOS 13… If this is a real issue for you your best bet would be to buy a second-hand iPhone running the version you require, but remember you won’t be able to recover your latest backup of your iPhone onto the new device without updating the iOS software too.

How do I undo an iOS update?

Click “iPhone” beneath the “Devices” heading in the left sidebar of iTunes. Press and hold the “Shift” key, then click the “Restore” button in the bottom right of the window to choose which iOS file you want to restore with.