Can we have power of attorney applicable from past date

1.As you mentioned that your sister and wife are owner of the property and they have signed the agreement. So as per the payment clause, the rent must be paid to the owners to the contract. Incase you desire to get the POA for the purpose of collection of rent or tenancy affairs , then you can request your sister in law and wife to execute a Special Power of Attorney which must clearly specify the authorization which they intent to give you.

2. Further the Power of Attorney cannot be valid from back date and it is suggested that you execute on the fresh/ current date. At the same time, make an addeum to the Lease Rent agreement specifying about the POA and the authorities granted to you. This will give you authority to collect rent and carry other management of tenancy affairs.

3.The value of stamp paper should be Rs.100 and if the Lease Deed is 11 months then you can simply notarize the same. But if the it is beyond 11 months it suggested that you get the same registered before the Sub registrar.