Hi,

The eligibility you should meet to get ews certificates is as follows:

• Candidate's annual family income must be less than Rs. 8 lakhs per annum.
• His family must not own more than 5 acres of agriculture land.
• The residential flat area should be below 1000 sq ft.
• The residential plot's area should be below 100 square yards if in a notified municipality sector.
• The residential plot's area should be below 200 square yards if in a non-notified municipality sector.

You can get the EWS certificate from your local government authority (Tehsil). The certificate is called an 'Income and Assets Certificate', and this is the proof that is required to avail the EWS reservation. The designated authority will verify your documents and issue your EWS certificate.

however once you have applied for ugc exam and results has declared you can not change your category now, since score and rank is availed based on the persons category.

hope it would help.