These Regulations shall be effective following adoption by the City Planning Commission and by Council, after public hearing and certification to the Recorder as provided by law. Henceforth, any other regulations previously adopted by Council or the Planning Commission shall be deemed to be repealed. These Regulations shall in no way affect any subdivision having received preliminary approval by the Commission prior to the effective date, provided, however, that no changes to the preliminary plan, as approved, are introduced by the subdivider.