Just bought a used 2010 CTS 4. 3.0l

Pressed the "lock" button on key fob twice. The car started. It has a 4 button key fob.
I didn't know it had remote start, and neither did the salesman.

The issue: Is this option factory installed or is it aftermarket installed from the last owner?
Next issue: I want another key fob made, will it accept the process of pairing with the car simultaneously with the aftermarket remote start? Or will it have to be programmed with the aftermarket starting system first and then the factory stuff second. Or vice versa?

The remote start is kind of important to me as I live in the Pittsburgh area...

Thanks in advance, I hope I worded/explained this clearly.