Can the 2015 imac connect with mac mini m2 as a primary monitor?

No, because neither of those Mac's support the old cabled Target Display Mode requirements.

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

If you have an M2 Mac mini, then you will need to use a external display.

see > Connect a display to Mac mini - Apple Support

iMac Late 2014 was not a TDM-support iMac. The last iMac with TDM support was the MID 2014. Please see the article that den.thed posted twice.

Apple start the deprecation of Target Display Mode in Late 2014 and threw the last shovel of dirt in its face in early 2020. It is very dead tech.

bhaskargaddam wrote:

The mac i have is 2014 late

That would be a 27" Retina 5K iMac – the first of its kind. Target Display Mode went away when that iMac came out, and never returned.

So restrictions on the M2 Mac mini aside, neither your Late 2014 iMac nor your 2015 iMac support TDM.

No, because the M2 Mac mini can not use any iMac as a display.

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