The provisions of this Act which amend the Code of Criminal Procedure, 1898 so as to alter the manner in which, the authority by which, or the law under or in accordance with which, any powers are exercisable, shall not render invalid any notification, order, commitment, attachment, bye-law, rule or regulation duly made or issued or anything duly done before the commencement of this Act, and any such notification, order, commitment, attachment, bye-law, rule or regulation or thing may be revoked, varied or undone in the like manner, to the like extent and in the like circumstances; as if it had been duly made, issued or done after the commencement of this Act by the competent authority and in accordance with the provisions then applicable to such case.