macOS upgrades
I have an iMac with Catalina 10.15.7 how do I upgrade to macOS Big Sur?
The model year of an iMac is available at Apple menu > About This Mac.
A late 2012 through late 2013 iMac can be upgraded to Catalina 10.15.7 but no later. See: How to download macOS - Apple Support
A mid 2014 and late 2014 iMac can be upgraded to the latest version of Big Sur macOS 11 but no later. See: How to download macOS - Apple Support
A late 2015 iMac can be upgraded to the latest version of Monterey macOS 12 or earlier but no later. See:How to download macOS - Apple Support
A 2017 or later iMac can be upgraded to the current version of Ventura macOS 13 or earlier. See: How to upgrade to macOS Ventura - Apple Support