Connectivity
What cables are required to connect late 2014 Mini to iMac display
What cables are required to connect late 2014 Mini to iMac display
Note that the iMac must be an early 2014 model or older. Late 2014 iMacs and newer have dropped the ability to be used as a display.
Yes, I believe they must both be running the same MacOS, preferably Big Sur or Monterey. If the Imac has thunderbolt 2 then you could use that, that is what is on the Mini late 2014. Need to know year and screen size of Imac.
Connectivity