If agreement for sale is executed by builder and full consideration has been paid by you and agreement mentions possession has been delivered it has to be stamped as conveyance 

2) in other words agreement for sale is treated as sale deed 

3) as far as circular mentioned by builder ask him to furnish copy of the circular relied upon by him 

1. It's true that the stamp duty paid on the agreement for sale will be adjusted against the stamp duty payable on the sale deed within three years, subject to the seller and the buyer are the same, schedule of the property is also the same. If the above condition is different, then the stamp duty paid now on the agreement for sale will not be adjusted against the stamp duty payable on the sale deed.

2. If you could pay the admissible stamp duty corresponding to the stamp duty for registering the sale deed now itself, then get the sale deed registered in your favour now itself instead of getting the agreement for sale registered at a later date.

Any agreement of sale with possession is chargeable as “Sale,” but where subsequently sale deed is executed in pursuance of an agreement of sale, the stamp duty paid on agreement of sale shall be adjusted towards total duty leviable on the sale deed. Article 47-A, Explanation-I Stamp Act.

Agreement to sell is different from sale deed. Do not register the sale deed unless the oc cc certificate has been obtained by the builder and the flat is ready to move in. Stamp duty payable on the sale deed is different from stamp duty on the agreement to sell.

Dear Client, 

Stamp duty paid on the sale agreement will be adjusted against the sale deed, you will not have to pay stamp duty again. 

Thank You 

These stamps are liable to be adjusted towards the total stamp duty payable on this sale deed.  The stamp duty paid under the agreement to sale, is part of the stamp duty that is payable at the time of execution of sale deed, hence it is adjustable whenever the sale deed is executed subsequent to the execution of the sale agreement 

- If you are paying the full stamp duty of the said property , then sale deed can be executed in your favour, and registration of sale agreement is not necessary . 

- However, as per Article 47-A, Explanation-I Stamp Act it is true that if a sale agreement with possession is registered , then the stamp duty is adjustable on the sale deed . 

if you have paid stamp duty at the time of registration of agreement to sale then you need not pay stamp duty again on sale deed. That is the rule. You will just need to pay the nominal amount which is between 500-1000 depending on your state.

It's illegal you don't need any circular