Seller denying to sell the property

Of course, a further line of action is your choice.

The excuses given by the seller are all lame excuses.

If you wish to teach a lesson to the recalcitrant seller, seek a specific performance of sale as per the unregistered agreement. But your advance of Rs.1.00 lakh gets blocked with him, which he may try to give back to you by cheque or by depositing it into your account by way of online transfer since he knows your bank and account number including IFSC Code as you paid advance through cheque or he may deposit the amount in Court stating that he is no longer interested. If you accept the amount back by cheque or online transfer, your case has only the value of your getting inconvenienced and the demand for specific performance may lose much of the wind to its sail.

Now you have to decide to weigh all the pros and cons of the matter including the seller deciding to deposit the advance in Court and the ultimate time Court takes up the case and eventual judgement in your favour at which time also it is not known how much damages Court may award and whether such award is commensurate to the trouble you are taking and further expenditure you have to bear in the process. 

All the best to you.

Basically you have not entered into a proper sale agreement with the vendor.

The document on a white paper is just a stamped acknowledgment for the amount he received.

Even if you approach court, the court may pass an order for refund of the advance amount he received with interest @ 6% p.a. and you may have to pay the court fee more than the interest amount.

If the vendor is willing to return the booking amount, you may better accept the same and ignore other issues. 

You cannot even file a suit for specific performance of contract based on the so called agreement in your possession because it is not at all an agreement, hence the court may not even entertain your suit for specific performance of contract, hence think it over and take a wise decision at right time instead of unnecessarily dragging the issue and getting more stressed or becoming more anxious over this every day.