If the iMac 2015 appears as listed to Qualify.
Then, Yes it can run macOS 12 Monterey
macOS Monterey is compatible with these computers
Though the current Apple Silicon MacBook Air 2022 machine could not be used for this purpose
Notation: If the computer being used to perform this action is Too New to qualify to run the version of macOS - this computer can’t be used.
Alternative is, to gain access to a Qualifying Apple Computer from a family member, friend or associate.
If you can access another machine that is Intel Based and qualifies for Monterey
Detailed instruction after successfully creating the Monterey USB Bootable Installer Drive
Shutdown computer and disconnect all external drive Except the newly created Bootable Installer.
Restart and immediately hold the OPTION key until the Startup Manager appears and choose the USB Drive.
It will present options >> Disk Utilities >> View >> View ALL attached Drives.
Choose the Upper Most Drive ( not the volumes indented and list below ).
The drive normally is called Apple Media or Apple SSD - that is the drive to Erase and format as APFS with the GUID Partition Map.
Once that is done >> backup out of Disk Utilities and choose install macOS.
Follow the prompts and it may automatically reboot several time.
Upon a final reboot - Setup Assist will present with the newer version of macOS.
