I meant to update my G5 to the 8.20 and accidentally downloaded and installed the experimental 8.30. Can I simply download the certified 8.20 and fix it?
Because it's higher version than the certified, you'll have to do something slightly different, but it's no big deal. You'll need to follow section 7.3.3 of the G5 Maintenance Manual : https://static.garmin.com/pumac/190-01112-11_10.pdf "The following procedures should be followed if a later version of experimental G5 software has been loaded to the G5 Certified unit."