The 2011 iMacs can run El Capitan, Sierra, and High Sierra – but reportedly will not be able to run Mojave.
Photoshop CC requires Mac OS X 10.11 (El Capitan) or later. Was only going to use it for lightroom, photoshop, web browsing and college work.
So I was looking at picking up a second hand imac mid 2011. I have a main pc but I find it hard to edit on a tn monitor.