Any person appointed by His Majesty to act as Governor-General or as the Governor of a Province during the absence of the Governor-General or the Governor from India, or during any period during which the Governor-General or the Governor is for any reason unable to perform the duties of his office shall during, and in respect of, the period while he is so acting have all the powers and immunities, and be subject to all the duties of, the Governor-General or Governor, as the case may be, and, if he holds any other office,_ shall not act therein or be entitled to the salary and allowances appertaining thereto while he is acting as Governor-General or Governor.