Hello,
In case the two caste certificates have the same information but different RD numbers, officials can verify either of them. The certificates don't need to be in a certain language (Kannada or English). Have originals as well as duplicate sets of both with you, and if given the occasion, make the officials aware that the RD numbers differ, but the details are the same. The English certificate might be more acceptable for NEET/KCET.