1. You are not supposed to take possession of an incomplete flat,
2. You are also not supposed to take possession of thef lat till completion certificate issued by the local Municipality/Corporation is obtained by the builder and copy handed over to you,
3. send the builder a legal notice to this effect claiming damages,if things are not rectified within 30 days,
4. If there is no change in the matter, file a consumer case before the local Consumer Dispute Redressal Forum alleging deficiency in service and unfair business practice claiming immediate completion & registration of the sale deed of the flat on receipt of payment from you, damages, interest & cost.