selection

What is the mistake?Please frunish the information.

There are still several understanding people left in India, and they can excuse genuine slips or mistakes if properly explained.  I am surprised as to how one can commit a mistake in enclosing a copy of the caste certificate ???  You can not do anything except defending on your actions and it is left to them to decide as to whether you have misrepresented facts and gained an advantage in recruitment or not.

actually they want caste certificate between 2016 and 2017 Meanwhile I have the caste certificate of that range and another caste certificate of 2014 ,I have verified the right original copy but at time of Xerox copy of document submission by mistake 2014 caste certificate was placed in file so when the entire Xerox copy cross verified in board level they rejected my candidature

You can approach recruitment board officers and submit as they required with requesting letter to consider again.

The defect, as posted, is curable. Caste or community of a person does not change with passage of time. You may represent; if unsuccessful may seek judicial review if so advised.

The defect is serious as it is concerned not with just caste but connected with the 'Noncreamy layer" certificate.  If you are having such certificate there is nothing wrong in representing a fact, admitting a mistake and praying to view the matter leniently and not to cancel the selection as the latest certificate was also obtained and there is no wilful mistake or suppression of material facts to derive undue and illegal advantage.  Wait for their response. If you are having financial capacity contact a local advocate as the reaction of the employer is too harsh and you can even approach HC for viewing the matter leniently.

You have handed the matter to your advocate for filing a writ before High Court four months back and due to the COVID 19 the writ was not filed..( As reported by you in another thread) .what you wish to do more under these circumstances for a remedy ??? The most competent is certainly the advocate that is well versed and handling the issue in High Court...