Gst in joint venture land devlopment agreement

 In a joint venture Land Development project, for construction of residential units ( 50% : 50%).( assume there are 10 units to be made , selling rights of Nos.5units  with the Builder and  Nos.5 unit with the land owner ).

 Accordingly Builder makes all purchases, renders all services at site ,gets all purcahse /services bills in the name of  Builder, with input GST on construction activity of all units  ,

 Now at the time of selling , The Builder has input bills of all residential units (10 Nos.in this case), while selling his predefined resi.units(5 Nos.in this case) to third parties, can Builder  get setoff of GST all input (10 units)on part units (5 units)while  selling ?

can land owner charge entire GST  on his share built units, from third parties ( Nos.5 in this case)? as per joint venture land development agreement?

if yes , is it necessary for land owners to be registered under GST? and to file GST returns, but there is No materialistic input by him, what input GST that he has to show?