44. Subject to any rules made under this Act- (a) a Board may, on an application made by any person interested or of its own motion], review any decision or order passed by it and pass such order in reference thereto as thinks fit; (b) an Appellate Officer may, on an application made by any person interested or of his own motion, review any decision or order passed by him or his predecessor and pass such order in reference thereto as he thinks fit: Provided that no order shall be varied or reversed unless an opportunity has been given to the persons interested to appear and be heard in support of such order.