If I have EWS certificate from center Government. Is it useful for admission through state quota admission?
Depends from State to State, but ideally it shouldnt be an issue as far as your document is a valid one and after the prescribed date. Like JOSAA expects you to have an EWS Certificate dated after 1st of April, of the present year. Hence, do check the official brochures of State Engineering Counselling carefully. All the Best.