I have a leak in the pipe coming from the toilet leading to the drain. I would like to replace this pipe, including a new flange on the bathroom floor. This pipe is cast iron and connects to a copper drain pipe. If I use ABS, can I connect it to the copper drain pipe?

If I use ABS, can I connect it to the copper drain pipe?
Yes you may, Use a Fernco Shielded Coupling,(see image) to convert from copper to plastic. Good luck, Tom