I just updated my imac to macos 12.3, but it stuck at apple logo screen... how can I go back to macos 12.2.1 ?

Hello fai236,

If your Mac is starting up to the Apple logo or progress bar, this page explains what to do: If your Mac starts up to an Apple logo or progress bar

Your Mac shows an Apple logo when it finds your startup disk, which is usually the disk built into your Mac. As startup continues, you should see a progress bar, with or without the Apple logo. This screen might alternate with a blank screen several times.

If you're installing macOS, the Apple logo or progress bar might persist for much longer than usual. As installation continues, the progress bar might move slowly and pause for long periods. That's why Apple recommends beginning macOS installation in the evening—so that it can complete overnight, if needed.

If your Mac remains stuck on the Apple logo, the "If your Mac is stuck on this screen" part of the above link goes over what steps to take.

Take care!

Fai236,

Were you able to review the steps in the previous article? It did include installation instructions.

If your Mac is stuck on this screenIf you think you've waited long enough to know that your Mac is stuck on this screen, follow these steps.1. Press and hold the power button on your Mac for up to 10 seconds, until your Mac turns off. Then turn your Mac back on.2. If the issue persists, press and hold the power button until your Mac turns off. Then unplug all accessories from your Mac, including printers, drives, USB hubs, and other nonessential devices. You could have an issue with one or more of those devices or their cables. Then turn your Mac back on.3. If the issue persists, once again press and hold the power button until your Mac turns off. Then use Disk Utility to repair your startup disk. * If Disk Utility found no errors, reinstall macOS. * If Disk Utility found errors and repaired them, restart your Mac. If the issue returns after restarting, reinstall macOS.4. If you still need help, please contact Apple Support.

Hopefully this helps.

Good Luck!