S. 10 (23C): Educational institution-Approval-Exemption claimed u/s 10(23C)(iiiad)-Only after receipt of approval u/s 10(23C)(i) r.w.s. 10(23C)(vi) for the relevant year-held, it was entitled to claim exemption u/s 10(23C) even though it was not registered u/s 12A[S. 10(23C(1), 10(23C)(vi), 12A]