Downgrade MacOS without second mac (M1)
I've successfully downgraded my mac when it softbricked, the solution was not easy to find. That's why I'm posting all-in-one tutorial here.
After flashing MacOS 12 (Developer beta) I've experienced issues with my XCode and homebrew. I needed to go back asap, beacause I need XCode for my school project.
I was dumb enough to not download big sur from app store while I was on the MacOS 12, I directly went to restore mode and erased my disk...
Then I discovered that I can't choose which MacOS version I will install, the only option was to reinstall the developer beta one.
After installing it again I was not able to create account, so I softlocked myself. Without a second mac I couldn't make a installation USB.
Downgrade from MacOS 12 to Big Sur
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Turn off your mac and then hold the power button until the "options" button shows. Click on it.
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Erase the main disk using disk utility
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Connect a removable drive (could be SSD or a USB Flash drive)
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Enter the following commands in the terminal
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cd '/Volumes/<name of your removable drive>' -
mkdir -p private/tmp -
cp -R '/Install macOS 12 Beta.app' private/tmp -
cd 'private/tmp/Install macOS 12 Beta.app -
mkdir Contents/SharedSupport -
curl -L -o Contents/SharedSupport/SharedSupport.dmg http://swcdn.apple.com/content/downloads/55/59/071-00696-A_4T69TQR1VO/9psvjmwyjlucyg708cqjeaiylrvb0xph94/InstallAssistant.pkg -
./Contents/MacOS/InstallAssistant_springboard
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Something strange will happen. It looks like you are reinstalling beta version, but actually it will install Big Sur.
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After Installing it, turn off the computer and go back to the recovery options
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Open terminal and enter:
resetpassword
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Dialog window will appear, in the bar select erase mac and then confirm it (blue link)
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Computer will reboot back to restore mode.
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Install our "fake" big sur again
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cd '/Volumes/<name of your removable drive>/private/tmp/Install macOS 12 Beta.app' -
./Contents/MacOS/InstallAssistant_springboard
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After installing you can finally log in and create recovery usb (You need to reinstall the system again to get rid of "Reinstall MacOS 12" in the recovery menu)