(4) No action or proceeding to recover possession pursuant to this subdivision shall be commenced in a court of competent jurisdiction unless the owner shall have served the tenant with a termination notice in accordance with section 2524.2(a), (b) and (c)(3) of this Part.
(5) The failure of the owner to utilize the housing accommodation for the purpose intended after the tenant vacates, or to continue in occupancy for a period of three years, may result in a forfeiture of the right to any increases in the legal regulated rent in the building in which such housing accommodation is contained for a period of three years, unless the owner offers and the tenant accepts reoccupancy of such housing accommodation on the same terms and conditions as existed at the time the tenant vacated, or the owner establishes to the satisfaction of the DHCR that circumstances changed after the tenant vacated which prevented the owner from utilizing the housing accommodation for the purpose intended, and in such event, the housing accommodation may be rented at the appropriate guidelines without a vacancy allowance. This paragraph shall not eliminate or create any claim that the former tenant of the housing accommodation may or may not have against the owner.
(b) Recovery by a not-for-profit institution.
(1) The owner is a hospital, convent, monas tery, asylum, public institution, college, school dormitory, or any institution operated exclu sively for charitable or educational purposes on a nonprofit basis, and the owner, upon notice to the tenant in accordance with section 2524.2(c)(4) of this Part, requires the housing accommodation for its own use in connection with its charitable or educational purposes, and either: