Builder has to deliver possession after issue of OC

2) since builder has not done so not entitled to charge holding charges 

On the contrary you can demand refund with interest . Complaint to RERA. And if builder still adamant , file consumer complain for possession with compensation or refund with interest and compensation.

Builder cannot charge holding charges from you as the occupancy certificate and completion certificate of the flat has still not been issued.

you can file a complaint against him in consumer court for deficiency of services and unfair trade practices 

See.you can give notice or reply to builder that since there was delay in construction so builder is liable to pay you compensation for delay , you are not liable to pay holding xhqrges.

You can go too  consumer court for deficiency of service

Please check your agreement, if in the agreement your builder has asked you to pay such charges then you are required to pay. In case the agreement does not mention, then you can issue a legal notice  mention in the notice that you are not liable to pay any such charges as per the agreement.

Despite legal notice if he fails, then you can file a case before the consumer forum for deficiency of sevices.

the builder cannot claim holding charges after issuing NOC. generally the NOC has been issued after clearance of all dues so the NOC shows that you have no dues. you can file a complaint before the RERA authority for such illegal demand. 

No builder cannot claim holding charges as it was his failure that he have not completed the work on time. And it is unfair business practice by builder. 

You can file a complaint before the District Consumer Dispute Redressal Forum alleging deficiency in service and unfair business practice claiming relief, damage & cost.

But if he refuse to give you possession without payment of holding charges you should ask him to give reciept of the same before paying money and taking possession. After the possession is handed over to you you should file the complaint before consumer Forum. 

You may issue a legal notice to the builder to deliver possession of flat immediately since all the payments have been done and also the registration is also done, if he fails to respond or comply with the demand made you may drag him to the consumer forum for relief and remedy including compensation for the physical and mental losses you suffered.

1. As per the information mentioned in the present query, makes it clear that builder is now doing which is not there in the agreement also for sure.
2. This is grossly the misconduct at his end.
3. You should file a suit for restricting against him for asking money illegally without having any liabilities from your end now.
4. Rest, if can get the copy of the agreement then would be able to guide more precisely.