GST registration cancellation in case of builder

Whether the semi finished houses booked or installments are being received from customers?

Then you can cancel without any problems. As ITC have already been denied under new rates for real estate and you are planning to sell the units after their completion no GST was applicable forget about the turnover itself.

Go with cancellation.

Moreover just for knowledge GST is applicable only on supply. When there is no supply there is no GST. Secondly till units are not booked they are of the nature of immovable property (building) and GST does not cover tax on buildings (Schedule III). It is only when booking is done before completion that it gets classified as service and GST gets levied.