Affordable housing registration mandatory for GST rate 1% or not

My query is whether a builder has to first register his project under affordable housing scheme and then he can pay 1% gst on sale of flats or  irrespective of his registration under affordable housing scheme  if the builder is fulfilling the condition of 60/90 sq mtr and consideration less than Rs 45 lakhs then he can pay gst @ 1%?

Thanks