DOWNLOAD AN OLD VERION OF PHOTOSHOP CC 2017

Hello,

I'm curently running Photoshop 2020. However I'm want to get a copy of  Photoshop CC 2017 so I can run Knoll Light Factory. Creative Cloud Old Version Tab in the Settings doesn't go far back enough, but when I tested downloading an old version it said it would over write my current version of CC. I want have both version installed. Is this possible and how do you do it ?

Many thanks  ??