1. Does the "Agreement for Sale" means " Private treaty" in this case.?
It is not private treaty or any other meaning known to you. It is a simple agreement to ell the property to you by the vendor/seller for a consideration/amount. In this since the entire consideration amount has been settled/paid through a cheque, the vendor is liable to execute a registered sale deed to the buyer. If he reuses then he can be dragged to the court by a specific performance of contract suit seeking the relief of execution of sale deed, if he fails to do it then the court will arrange for the execution and registration as per law.
2. Was Bank supposed to give us "Sale Certificate" after "Agreement for Sale" was done?
The bank cannot give a sale certificate since the bank is not selling this property. The sale agreement was with the seller and not with the bank, however since the bank had recovered the money it has released the documents. If you deeply probe into matter you may find many more shocking news that the bank would not have seized the property at all nor it has brought the property into auction as is required by law.
The bank to wash away the responsibility has tained the amount from your father and adjusted it towards the outstanding loan and instructed the seller to execute a rgistered sale agreement to your father instead of executing the registered sale deed, may be because the seller would b required to pay more than the amount settled by yor father towards the sale of the property which your father would have agreed to pay at a later date. There may be many more shocking informations which would not have been rectified at that time due to the lethargicness of both the parties or may be that nobody bothered about it or took the issue of sale deed seriously.
3. Can we ask for "Sale Certificate" from Bank now and get it registered ? As we had already paid the Stamp Duty at the time of agreement, do we have to pay the Stamp duty again.?
In my opinion the bank would not have sold the property because the sale agreement was between the seller and your father hence bank may not furnish sale certificate.
The stamp duty what was paid during the registration of sale agreement was for that deed alone, you may have to pay the difference in stamp duty for registering the sale deed to that of the sale agreement deed.
4. If all above options are not possible, is there any way to avoid executing Sale Deed with previous owner as he is not cooperating and we dont want to go for filing performance suit, its takes 5-10 yrs.
Now we have got following documents
1. Society SHARE CERTIFICATE ,
2. Copy of commencement certificate ,
3. Copy of Occupancy certificate ,
4. Copy of CONVEYANCE DEED (mentioning our name)with the builder done at sub-registrar's office (which was done after we bought the flat.)
6.Original Sale Deed between Builder and Previous Owner.
7. Original Agreement of sale with previous buyer, Original Index , Stamp duty and registration receipt.
Everything is okay, but what about the title document indicating the title to the property.
A registered sale deed is the title document confirming marketable title to the property owner without which you cannot sell the property.
You do not do the same mistake what your father did.