going by the terms stated in the agreement of sale and agreement to build executed by the builder, the time for payment will be fixed as per the stage of completion (construction linked payment plan), if the agreement stipulates payment of the final or balance on completion of registration then irrespective of obtaining the OC the payment has to be made. Otherwise the builder can go ahead and cancel or terminate the agreement for non payment despite intimation.
Make the final payment and proceed for registration, if the builder fails to provide the OC (if accepted by builder to be provided) then you can proceed legally against the builder for non-compliance.
Non completion of amenities promised by builder in the said project will entitle you to seek compensation from the consumer court.
there is no question of any force being put by builder, but non-compliance by you will entitle the builder to cancel the agreement.
there is no other option but to register without OC