Hi Arun,
If I understand you correctly, your first question is whether or not you can change process notifications in such a way that it is different for different objects. If that is your question the answer is no.
If you are instead talking about the automatic notifications sent out by the ppm system for Risks and Issues, those are separate notifications from the process action item notifications.
All notifications that you are allowed to change are in the same Notifications section of the Administration area. You can search for each object to see which notifications you can change. Search for Issue if that is what you want, or Risk, or Process. The Process completion is indeed a notification you can modify.
You can find more information about configuring notifications in our Administration Guide:
https://docops.ca.com/ca-ppm/15-4/en/administration/configure-notifications-and-notification-templates
Jeanne