1. Dear member, reversion to lower post and consequent reduction in salary/wages are the legal issues and may result into industrial dispute/court case in view of the provisions contained under the approved Standing Orders of the establishment or as per principles of natural justice. Therefore, in my opinion, before proceeding for such action, suitable procedure is required to be followed by the employer/ disciplinary authorities.
2. There are no legal issues involved in respect of EPF and ESI in case an employee is reverted to a lower post or his salary is reduced. However, in case the said employee is not covered under above enactments, then he is required to be covered if his said reduced "wages" are within coverable limit as laid down under said enactments.
3. Rest, as suggested by (Cite Contribution) above, it would be more better if you share complete facts in the matter as above.