To get Graduation Degree Certificate after a long gap

This is a clear case of slow working of government offices. It is advisable to go for an RTI so that you will get the correct information. But before doing that in that city where the university is situated if you have any known persons you can ask one of them to visit on your behalf the university office and enquire the status.
When you file an RTI, you may get a reply stating what is the status of your application. But it may not ensure your certificate. So you have to see how to get the work done. Generally, in many government offices, unless otherwise, you go personally works may not be completed.
Once you file an RTI, there may be some moment and you may get a reply. You have already paid the money to be paid. I hope you have uploaded the receipt in the university site with your application form.

You can go for RTI and you will get a response also. But in parallel to that please send a letter with all the details to the Governor of the state and request him to intervene in the matter. By default the Governor is the chancellor of all the educational institutes in that state and he would direct the vice chancellor to do the needful and maybe your case gets expedited. If that does not work then you have to make an appeal to PMO office and as I have come to know in some cases PMO office is showing their displeasure to the offices or institutions for delay in the work. Many officials are having a fear from the name of the present PM who is dead against the delays and that might help you.