It is not at all a complex thing, in the interview call letter it is asked to bring the required documents in which following are mandatory

1. 10th certificate
2. Graduation degree and marksheet
3. Cgpa to percentage conversion formula
4. Any post graduation degree
5. Caste cerificate

All documents are asked in original with atleast one photocopy of each. Max 3 4 passport size photographs. They may also ask u to bring any specific document dor decleration of for TA claim.

They crosscheck every data that u entered at the time of filling the application with ur original documents and keed one self attested photocop y of each document.

In case, if u could not sow/submit any required document they will ask u to give a decleration for either submitting it within atime limit or submit it at the time of medical examination(if interview cleared).

I hope it will clear ur doubt.