I purchased my iMac in late 2012. The OS was Mountain Lion. Then I upgraded and kept upgrading it until now, to Catalina. But I have important music programs that work with my previous OS. How can I downgrade back to Mountain Lion? Please, help.
Downgrading your macOS to an earlier version will erase all the data from your drive and will require that you:
1) Back up your Mac with Time Machine (or other backup solution) to an external disk drive.
2) Have available an installer for the previous version. This can be a Time Machine backup made prior to your upgrade to the current version, or it can be a bootable installer for that previous macOS created on a USB flash drive. You can get old versions of macOS here. Optionally, a previous version may be available on an Intel-based Mac if you use Shift-Option-Command-R startup key combination during startup. You may be offered the macOS that came with your Mac, or the closest version still available
3) Boot your computer in macOS recovery mode and wipe the drive in preparation of reinstalling the previous OS.
4) Reinstall macOS on your computer using your prepared USB installer or the Time Machine backup made with the older macOS. You may also reinstall the macOS version that is offered at the macOS Utilities screen after booting in Recovery mode.
Downgrading your macOS to an earlier version will erase all the data from your drive and will require that you:
1) Back up your Mac with Time Machine (or other backup solution) to an external disk drive.
2) Have available an installer for the previous version. This can be a Time Machine backup made prior to your upgrade to the current version, or it can be a bootable installer for that previous macOS created on a USB flash drive. You can get old versions of macOS here. Optionally, a previous version may be available on an Intel-based Mac if you use Shift-Option-Command-R startup key combination during startup. You may be offered the macOS that came with your Mac, or the closest version still available
3) Boot your computer in macOS recovery mode and wipe the drive in preparation of reinstalling the previous OS.
4) Reinstall macOS on your computer using your prepared USB installer or the Time Machine backup made with the older macOS. You may also reinstall the macOS version that is offered at the macOS Utilities screen after booting in Recovery mode.
Downgrading from Catalina to Mountain Lion
