Hi Mayur,
Not sure which certificate plugin you mean. There are several plugins that have certificate in their name.
The one I know best is the "Certificate module". Look at MoodleDocs here. It has fields for date of issue, and signature. Read MoodleDocs on how to customize a certificate here.
Was is the "content of course" data? Do you mean the course description?
While anything is possible in Moodle, some of what you want probably means altering the php code in places not mentioned in the documentation. I think creating the string that contains the course description or custom user_fields might be another complicated thing to do that needs someone with PHP skills and knowledge of the Certificate code.
Hope this helps you get started,
Chris