Value of agreement made in stamp paper

Hi I would like to take experts view on below mentioned issue. Kindly share your valuable advise/thoughts/comments. Ravi bought an agricultural land in Tamil Nadu in 1995. From the main road, it has no defined way/route to reach the land. There is one land in between the main road and Ravi's land which is belongs to Sekar. In 1996, Ravi and Sekar made an agreement in front of village Panchayat people to allow Ravi to access his land thru Sekars land. The agreement made in Two Rs.10 stamp paper with additional sheets stating that Sekar will leave widdth of 10 Feet way from the main road to till Ravi's land. In this area both the parties should not cultivate any crops. Now the question is Is the agreement made in stamp paper valid? Can it be used as a legal document? If Sekar sells his land to any other party, is this agreement still valid? Sekar signed an agreement to allow Ravi to accesses his land. If Ravi sells his land to other party, is there any issue? Is the agreement made on stamp paper mandate to register on Registrar office? If Sekar refuse to obey the agreement, is any legal action can be taken on sekar by Ravi? Agreement made on stamp paper. It is a physical item and has life time and chances to get damage. Is there any suggestions to make it safe? (Like registering somewhere so that I can get a authenticated document at any point of time) Finally, if Sekar denies to as he agreed, how to approach it. Kindly share your comments. Looking for your valuable advises and suggestions. Thanks in advance.