(1) In any suit or proceeding against any ¹ *** member of the Force for any act done by him in the discharge of his duties, it shall be lawful for him to plead that such act was done by him under the orders of a competent authority.
     (2) Any such plea may be proved by the production of the order directing the act, and if it is so proved, the ¹ *** member of the Force shall thereupon be discharged from any liability in respect of the act so done by him, notwithstanding any defect in the jurisdiction of the authority which issued such order.
     (3) Nothwithstanding anything contained in any other law for the time being in force, any legal proceeding, whether civil or criminal, which may lawfully be brought against any ¹ *** member of the Force for anything done or intended to be done under the powers conferred by, or in pursuance of, any provision of this Act or the rules thereunder shall be commenced within three months after the act complained of shall have been committed and not otherwise; and notice in writing of such proceeding and of the cause thereof shall be given to the person concerned and his supervisory officer at least one month before the commencement of such proceeding.