Stamp duty requirements vary by location and the nature of the agreement. In India, stamp duty is levied on the value of the agreement and varies from state to state.
Assuming you are in India, if the agreement you are making is a monthly payment plan for a year with each payment being 35,000 INR, the total value of the agreement would be 4,20,000 INR (35,000 INR x 12). To determine the required stamp duty, you would need to check with the state government where the agreement is being executed, as each state has its own stamp duty rates and requirements.
Regarding the possibility of having one agreement for the whole year with details filled in for each month, it is possible to have such an agreement, provided that it is executed correctly and meets all legal requirements. However, it is important to ensure that the agreement is clear and includes all necessary details, such as payment terms, due dates, and consequences of default, to avoid any misunderstandings or disputes later on.