Older house with copper pipe drain from shower. I was not able to get the drain apart so I cut the shower floor apart, and still not able to get shower drain apart. If I cut pipe can I use PVC pipe with the copper pipe that is already there?

Sure, you will just need to get a copper by pvc shielded adapter clamp to make the transition.

Why were you removing the shower drain in the first place? What, exactly, are you trying to accomplish? Back to you, Tom