Gu Xiaolan's ability to restore the White Long Sword indicates that the root of the Mutant Cosmic Rules cannot completely alter the physical properties of items; its impact on external cosmic objects is also limited and can be reverted.
Gu Xiaolan easily reverses the physical properties of the White Long Sword because the sword has long been integrated with her. The two are constantly in a state of close contact, allowing her to use the energy within her to revert the White Long Sword. However, if Gu Xiaolan attempts to reverse items altered by the root of the Mutant Cosmic Rules, she does not possess that ability. For example, with this Metal Wooden Door, Gu Xiaolan has no solution.
