Fresh install of the system software on a 2009 iMac
How does one install a fresh copy of the system software on a late 2009 iMac, which was manufactured one year before Apple offered the capability to reinstall the system software via a ⌘ / R restart? The computer in question is running macOS High Sierra 10.13.6.
I searched for an answer but could only find instructions for a clean install.
Was it even possible to reinstall a fresh copy of the system software then?
Many thanks.