Section 81W. A planning board, on its own motion or on the petition of any person interested, shall have power to modify, amend or rescind its approval of a plan of a subdivision, or to require a change in a plan as a condition of its retaining the status of an approved plan. All of the provisions of the subdivision control law relating to the submission and approval of a plan of a subdivision shall, so far as apt, be applicable to the approval of the modification, amendment or rescission of such approval and to a plan which has been changed under this section.

No modification, amendment or rescission of the approval of a plan of a subdivision or changes in such plan shall affect the lots in such subdivision which have been sold or mortgaged in good faith and for a valuable consideration subsequent to the approval of the plan, or any rights appurtenant thereto, without the consent of the owner of such lots, and of the holder of the mortgage or mortgages, if any, thereon; provided, however, that nothing herein shall be deemed to prohibit such modification, amendment or rescission when there has been a sale to a single grantee of either the entire parcel of land shown on the subdivision plan or of all the lots not previously released by the planning board.

So far as unregistered land is affected, no modification, amendment or rescission of the approval of a plan nor change in a plan under this section shall take effect until (1) the plan as originally approved, or a copy thereof, and a certified copy of the vote of the planning board making such modification, amendment, rescission or change, and any additional plan referred to in such vote, have been recorded, (2) an endorsement has been made on the plan originally approved as recorded referring to such vote and where it is recorded, and (3) such vote is indexed in the grantor index under the names of the owners of record of the land affected. So far as registered land is affected, no modification, amendment or rescission of the approval of a plan nor change in a plan under this section shall take effect, until such modification, amendment or change has been verified by the land court pursuant to chapter one hundred and eighty-five, and in case of rescission, or modification, amendment or change not so verified, until ordered by the court pursuant to section one hundred and fourteen of said chapter one hundred and eighty-five.