If you have given limitation period in the notice than you can sell the property if he does not respond to the notice.

1. it is not safe to make any agreement which is silent about the competition of sale and hence the purchaser is taking advantage of it by dragging the purchase.

2. hence you will have a send them a written notice asking them to complete the sale within a  time frame.

3. If he defaults to purchase the same by making full payments, you can cancel the agreement by refunding the advance money, if paid.

You should refund earnest money received by you  and then sell property to third party 

take plea that as buyer failed to make balance payment inspite of repeated reminders property was sold to third party 

Even if no time is mentioned it means within a reasonable time period. This cannot mean thatvyou have to wait forever. Give him a notice and go ahead with the sale if he doesn't respond.

Issue notice to the said buyer asking him to pay balance sale consideration and complete the transaction within one week from date of receipt of notice, stating that inspite of requesting / demanding you failed to complete your part of obligation.  Failing which you can go ahead. 

You cannot wait for eternity.

If the AOS does have forfeiture clause you can forfeit the advance, else you have to refund the advance received by your father.

1.It is legally necessary to issue a Legal Notice to the Buyer party, rescinding the Agreement, due to his failure to honor the Agreement, by giving him another opportunity with time limitation to make balance payment.

2. Subsequent, to above, after the Notice period, you will be able to execute Sale Deed with the New buyer party, without any legal reference to the earlier buyer party.  Here even If the earlier buyer party exercises his legal options, he will not be able to succeed, more so since Four years have lapsed since the original agreement.

Dear querist,

To want specific performance of the contract with the buyer you need to file a suit for specific performance and in case you dont want it now due to lapse of lot of time, A legal notice of intimation can be served on him along with a public notice which will suffice your requirement. 
We will be providing them a specific time period after which we can sell that property.

They might be a continuous follow up required for the same.

you can contact me for sending the notice of intimation on your behalf or to file a suit.

 A thorough search of my name on google with the keywords” Advocate Yuganshu sharma” might be sufficient to get my contact no.

regards,

Yuganshu Sharma

Advocate

Delhi high Court

you may cancel the same by issuing a notice to the buyer and refunding advance amount to his/her account by paying amount if the agreement term has not been completed..

Generally a sale agreement is valid only for three years from the date of its execution.

The buyer's case may not be maintainable even if he approaches court with a suit for specific performance of contract beyond three years, hence you may proceed with the sale of property by issuing a public notice in this regard.

You can sell it as you have done your part. He needs to come forward. 

- As per law, the limitation period of agreement to sell is maximum 3 years from the date of execution, or the time period , which is mentioned in the agreement.

- Since, 3 years period has already passed, and no time mentioned in the agreement , hence legally you can sell it legally , to any third person as per wish. 

- However, if you want to issue a public notice for the same , then it will be considered as an extra time give to the buyer .

- Better issue a notice /information to the said buyer, and thereby mentioned that you are ready to execute transfer documents in his favour , if he will approach within a period of one week from the date of receipt of the notice , otherwise you are constrained to sell it to the third party. 

1. Send a notice for cancellation of agreement on ground of non payment of consideration to purchase the property and delaying the agreement for 4 years. 

2. Also send him the copy of public Notice for cancellation of agreement and give him a time of 30 days to pay consideration and registration of property.

3. You can also offer him to refund the amount taken as token money. 

No need of any public notice. Just go ahead and sell the property before it came in knowledge of buyer. When their is no time mention in agreement, than it is to be performed within reasonable time.

Forfeit the token.

1. If there is no time mentioned in the agreement to sell for execution of sale deed then limitation period to file a suit for specific performance begins from the date of agreement itself.

2. Before selling it to another buyer you should serve a lawyer's notice for cancellation of agreement to the previous buyer. 

3. He can go to court but he will have to prove his willingness and readiness.