(a) acquired by the owner-applicant prior to January first, nineteen hundred seventy-one; or
(b) acquired by the owner-applicant through devise or intestate succession; or
(c) not at the time of acquisition of title by the owner-applicant, a part of a subdivision, as such term is defined in section eleven hundred fifteen of this title. In addition, this section shall apply to a single residential lot which the appropriate department deems proper for approval because of hardship or other special circumstances established to its satisfaction by the owner-applicant.