Once a nonconforming use or structure has been changed or altered so as to comply with the provisions of this Ordinance, it shall not revert back to a nonconforming use or structure. Once the Board of Adjustment has permitted the substitution of a more or equally restrictive nonconforming use for an existing nonconforming use pursuant to the provisions of section 12.56.050(a)4, the existing use shall lose its status as a legal nonconforming use and become subject to all the conditions required by the Board. [Code § 12.28-9.]