what MacOS is compatible with iMac 21.5 inch, late 2012
what is the latest MacOS compatible with my iMac?
iMac 21.5″, macOS 10.12
Question marked as
iMac (21.5-inch, Late 2012) supports up to macOS Catalina 10.15.7.
macOS Catalina is compatible with these computers - Apple Support
You can upgrade to macOS Catalina with the App Store on macOS High Sierra or older, or in System Preferences on macOS Mojave.
How to get old versions of macOS - Apple Support