The builder cannot refuse the said the agreement. Actually the BBA will contain the terms and conditions of the property to be purchased. This will specify the liability of the builder as well as the buyer and the conditions for breach of contract.
You should insist the builder to provide you with the said agreement. It is incorrect to say that the builder buyer agreement is not existing in UP as per the quoted law, it is still very much effective but the said rules are applicable for a different sector construction .If the builder is not cooperating you may ask him to terminate the contract and refund the entire amount because he is not obliging as per rules.