You can give a complaint with RERA against both. 

You can drag the new company to consumer forum for relief and remedy. 

You can file a suit for specific performance of contract against new company and implead the old one as necessary party to the suit. 

Before that first issue a legal notice to the new company demanding execution of registered sale deed in favor of you. 

File complaint against Migsun before consumer forum and seek orders to direct builder to execute registered sale deed in your favour ,to deliver possession of shop within stipulated period 

also seek litigation costs and compensation for mental torture undergone by you 

legal fees vary depending upon lawyer engaged by you 

You can start by serving a legal notice to Migsun to give the possession of the shop bought by you within the agreed upon time and to do the registration of the same in your name.

If they fail to adhere, you can file a complaint against them in consumer court or RERA to get the possession of the property, registration in your name, interest for delay, compensation and litigation expenses.

Filing case against Ansal would not be of much use in the facts of the case as they've already settled with you and have settled their dues.

You can also file a police complaint against Migsun for the offence of cheating and criminal breach of trust. 

Liability of delivery of possession of constructed structure is transferred from Ansal to Magnum. You can enforce your right to property against Magnum. No use appearing in NCLT. File a complaint in District Consumer Commission under new Consumer Protection Act, 2019 against Magnum adding Ansal as party. District Consumer Commission will issue direction to both either to give possession or refund the  consideration paid with interest and penalty. This is a clear case of cheating. You can also file a criminal complaint  in the  Court of Magistrate  for cheating against both. Court will direct police to investigate, register FIR, produced the  accused in Court, submit charge sheet and after trail convict the  accused. Punishment  for cheating is imprisonment  up to seven years. Offence is compoundable, you settle with Magnum and Ansal and withdraw the  complaint .

If the property comes under RERA registration, than better to file complaint with RERA. 

Regarding Migsun better to solve problem by meeting with Ansal, Migsun and you at same table, Because you are already getting late to get property in your hand. If you go into court it will be more complicated situation of litigation for one more property for you.

Now answers to your questions:

1) Please let me know how can I proceed further. 
Answer: you have choice of above solution or below any one of it.

2) What kind of case i can file on Migsun to take possession of my property?
Answer: Before filing case against Migsun, do you have sign any contract with them or its just oral contract between Ansal, Migsun and yiu.



3) Can I file case against on Ansal which is already in NCLT ?
Answer: No, You have already received credit note from him and you have accepted that too with Migsun.


4) Can I file police complaint again Migsun owner?
Answer: Need to check whether Migsun has done breach of contract according to the agreement with you.


5) What will be roughly expenses in case and how much time it will take to resolve?
Answer: 3% is court stamp duty and plus legal registration charges of court. Additional lawyers fees depending upon his/her experience mostly 20% of property amount may be charged.

- Since, Ansal API project already transfer to Migsun , and the Migsun dully accepted your deals then Migsun is under obligation to refund the amount to you.

- You can send a legal notice to the Migsun for asking the refund and to register the property in your name. 

- If no positive response then file a compliant before the consumer forum against the Migsun after making second party to the Ansal API. 

- Police complaint will not solve the issues related to property. 

- Expenses depend upon the lawyer to whom you will engage. 

Dear client I am sorry to hear that but in this case you may approach the Rara Court and complaint against the Builder to them

BBA with Ansal is your document which continues with Magnum. Basing you complaint  if BBA with Ansal file a complaint in District Consumer Commission under new Consumer Protection Act, 2019 under which  proceedings are very fast. You have option of approaching RERA Authority, but RERA takes much time in adjudication of claim. Further Authority under RERA does not have much teeth. In case of failure of comply it direction, District Consumer Commission can order arrest of builder.

You can approach RERA as well as consumer forum simultaneously.

You can implead both as parties because both have aggrieved you and both have caused you the grievances and damages.

File complaint against builder before RERA 

it would not slow down case 

Having no BBA is not your fault and would not slow down the case since you have other documents like allotment letter and payment receipt to prove that transaction.

You can approach either of the above-mentioned forums but in my opinion RERA would help in a faster resolution.

- You can approach the Consumer Forum against both the parties . 

Dear client You can seek any one if the remedy 

Its better you go to consumer court in above case