If charges are imposed by government you are liable to pay the same 

2) Pratikar charges is for builders who got land from authority at cheaper price 

Yes, as Govt has imposed on project so you are liable to pay proportionate dues. 

There are instances that the buyers have objected and agitated over this demand made by the builder and have even approached Consumer forums to get their grievances redressed in this regard. Actually Pratikar charges is for builders who got land from authority at cheaper price but later supreme court ruled to increase compensation to farmers.

The builder cannot demand the extra charges from the buyers if he had already availed the privileges from the government, because he had not extended the same to the buyers, hence let the builder make his own arrangement or you can approach consumer forum with a complaint and gather all the affected people in this connection and file a case collectively, the pressure of which may bring the builder to a negotiation platform and then your can negotiate the quantum.

- Legally , the buyer is not responsible  for the payment of Pratikar charges , and the builder is under obligation to pay the same due to getting the land on cheaper rate. 

- Further, as per the RERA Act, if the builder is delaying in construction & delay in possession, then the builder will have to pay 10% interest on the value of the property for delayed possession of flats.

- Hence, since, the said builder has failed to delivers the possession of the flat to you on time, then you can file a complaint before the consumer forum or under the provision of RERA for claiming 10% interest and the possession. 

Builder have to pay.

No you are not 

Dear Client,

Legally, the buyer is not responsible for the payment of Pratikar charges; instead, it is the builder's obligation to cover these costs due to obtaining the land at a lower rate.

Moreover, in accordance with the RERA Act, if the builder delays the construction and possession of the property, they are liable to pay 10% interest on the property's value for the delayed possession of flats.

Given that the said builder has failed to deliver the possession of the flat to you on time, you have the right to file a complaint before the consumer forum or utilize the provisions of RERA to claim 10% interest and demand possession of the property.