Urgent plz tax query

Please help me find a solution for the query

We sold property on sep 2006 for 35 lacs and incurred 15 lacs on development expenses.

6 months ahead to this transaction We purchased house for 20 lacs n now residing in the same house but the registration was not yet done but we entered into an agreement for the same. That is we took the possession n made the payment but registration alone is pending.

We claimed for exemption of this purchase cost from the sale proceeds is it valid exemption. Please guide me

Thanks in advance