OBC and OBC NCL are not the same. If your family income (excluding salary and agricultural income) is below 8 lacs per annum, then only you will be issued a OBC NCL (non creamy layer) certificate. IN our country, educational and financial benefits are given to only non creamy layer OBCs.if you apply to a central or state govt. institute, you will have to present an income certificate.And  as long as it is a valid obc certificate, you can present it anywhere,in state, even if the certificate has been issued in a different state.