Section 12. Uncompleted dwellings

1.  The  provisions  of  this chapter
  relating to new multiple dwellings  shall  not  apply  to  any  multiple
  dwelling for which plans were on file with the department or a permit to
  commence  building  was  issued  by  the  department  before July first,
  nineteen hundred fifty-two, or to any dwelling the plans for  conversion
  of  which  to  multiple  dwelling  occupancy,  were  on  file  with  the
  department or a permit authorizing the commencement of the work of  such
  conversion  was  issued  by  the  department before such date, provided,
  however, a certificate of occupancy as required  by  the  provisions  of
  section  three  hundred  two  shall  be  obtained therefor prior to July
  first, nineteen hundred fifty-seven.
    2. No provisions of any part  of  this  section  shall  be  deemed  to
  prohibit  the  amendment  of  any  plans  filed and approved before July
  first, nineteen hundred fifty-two, if such  amendment  would  have  been
  lawful  before  such  date,  or  if  such  amendment  complies  with the
  requirements of this chapter for alterations to buildings of  like  kind
  existing before such date.