Can I use thunder bolt 3 on a Mac mini m2 thunderbolt 4
Mac mini to iMac 2017
Question marked as
Yes Thunderbolt 3 and 4 are interchangeable, you can use Thunderbolt 3/4 to Migrate and for Target Disk Mode.
see > Adapters for the Thunderbolt 4, Thunderbolt 3, or USB-C port on your Mac - Apple Support
No if you are wanting to use the 2017 iMac as a Display for the M2 Mac mini in Target Display Mode.
carefully read > Use your iMac as a display with target display mode - Apple Support