The provisions of Article III of this chapter shall apply to all parcels of land legally existing on the enactment date of this chapter. Regardless of size, no lot subsequently subdivided from its parent tract shall be permitted to accommodate a new dwelling, except as provided for by § 375-3040C of this chapter. Similarly, subsequent owner(s) of any parcel of land legally existing on the effective date of this chapter shall be bound by the acts of previous owners in that such subsequent owner may only subdivide, for purposes of additional single-family dwellings, the number of lots, if any, remaining from the original number permitted by § 375-3040C of this chapter. In the event that a tract of land that was not classified as part of the AG Zoning District as of the enactment date of this chapter and was thereafter so classified, the size and ownership of such tract of land shall be determined as of the effective date of the change in the zoning classification.