I am Kandahar by caste in odisha.can I apply for once certificate

Hello aspirant, 

Khandyat is a caste in Odisha. Coming to your query, 

I'll suggest you to refer the central list for OBCs of Odisha :

http://www.bcmbcmw.tn.gov.in/obc/faq/orrisa.pdf

Also refer to state of OBCs and SEBCs list:

http://www.stscodisha.gov.in/Pdf/SEBC_List_Orissa.pdf

Good Luck.