reset to factory settings
how do I reset my 2015 imac to factory settings; erase all data
iMac 21.5″, macOS 12.7
Question marked as
To reset and erase all data on a Mac see instructions in What to do before you sell, give away, trade in, or recycle your Mac - Apple Support
Skip the "If your Mac has Erase All Content and Settings" section which only applies to newer Macs and use the other steps instead.