Hi Ahammed,
Thanks for clarifying. Unfortunately, information on the Custom Reports themselves, can't be extracted out of Rally. We don't have a REST endpoint for reports or custom reports and so essentially the reports themselves, along with their configurations, can not be extracted. You can see our API in this site: https://rally1.rallydev.com/slm/doc/webservice/ where you can see there isn't a Reports endpoint under the Object Model (on the left pane).
In my opinion, this is certainly a worthy enhancement request - to make reports available via the WSAPI . You are welcome to post this to our ideas site at: https://ideas.rallydev.com . This site requires a username. If you don't have a username then please email to: ac-ideas@ca.com and we shall create a username for you. Once posted, you shall follow up with your CA Account Team on the priority/progress of the enhancement.
My apologies that there isn't a better answer on this.
Sagi