Is it possible to connect a 2017 iMac to a Mac mini 2 to use as a display?

Sorry. Target Display Mode went away when the first 27" 5K Retina iMac came out in Late 2014.

There are third-party workaround products like Luna Display (Astropad) and Duet Display that might allow use of that iMac as a second screen, but they're not the same as a hardware connection to a standalone display.

If by Mac mini 2, you mean M2 Mac mini, then no. Get yourself a proper display (e.g. LG) for that purpose as 2017 iMacs are not supported for target display mode.

Nope, those Mac’s do not support the now obsolete Target Display Mode requirements.

carefully read > Use your iMac as a display with target display mode - Apple Support

There has not been an iMac manufactured for the last 10 years that can be used as a display with any Mac.

You're welcome.