I have 2010 iMac new unformatted unpartitioned hard drive and need to install older macos
suggestions? The Apple support options are unclear - particularly with how to create a bootable USB drive with installer and the iMac cannot do this on its own in current condition.
You can only create a bootable USB installer if you have another Mac that is compatible with the version of Mac OS X / macOS that you want to build the installer for.
If you have a bootable clone backup of the 2010 iMac – of if it came with optical recovery discs (it might have), that might be your best bet for running some version of the operating system, so you could start working your way back up. Note that even if you do manage to get the 2020 iMac running again, it cannot run any version of macOS that's more recent than High Sierra.
Rebuild old iMac OS or HDD replacement
