All non-testamentary documents duly registered under this Act, and relating to any property, whether movable or immovable, shall take effect against any order agreement or declaration relating to such property, unless where the agreement or declaration has been accompanied or followed by delivery of possession ¹[and the same constitutes a valid transfer under any law for the time being in force:
     Provided that a mortgage as defined in section 58 of the Transfer of Property Act, 1882 (4 of 1882), shall take effect against any mortgage-deed subsequently executed and registered which relates to the same property.]