ITC on goods sold by registered dealer to unregistered dealer

The considered opinion from group members is solicited on following :
Mr. A (not registered in GST) own commercial land and intends to build multi storied complex. He will sell part of the complex and hold some portion.
In sale deed, value for stamp duty purpose is not bifurcated in cost of land and construction cost. As per revenue, stamp duty is levied on type of shop i.e. location, space and floor.
The supplier of building material charges GST on the Supply..

Query : Will the GST paid by unregistered person would be cost of construction or he can claim refund of GST paid by him and could not be utilized later.
For sample purpose, I attach copy of sale deed.
Thanks ……..🙏