POA indirect sell

We have anchester's property in Mumbai and our family has name on the property card.However my Grandfather has given this property on 25 years lease in 1965. One of the clause in the lease was the lease will start only after the completion certificate/OC from BMC.The devloper who has taken this property on lease is modifying the plan every year or two and submit it to BMC , so indirectly trying to show that construction is not yet complete and the lease has not started.However there were almost 40-60 shops (tenants) and flat holder staying in that building. The lease holder is submitting the rent of Rs2000 every-month as per lease condition.He dont wish to leave possession because he earns lot of money with tghis property in Mumbai prime location. Now the scenario is another builder/promoter wish to opt this property as property card, 7-12 is still in our name.And he is asking for Genral power of attorney for sale purchase & mortgage and ready to give some money against this power and also told that the money is non -refundable and we will take care of rest of the financial & legal implications.He is ready to register the POA and one MOU mentioning the money transaction with applicable/full stamp duty as per law. My Questions are.. 1. If we register the POA and the MOU with him then is it possible to transfer the 7-12 on his name using POA & MOU ? 2. If he takes loan/mortgagee the property and makes the fault with bank , do we responsible for such misuse ? 3. what are other implications do you see in such indirect sell? 4. How safely this can be done if above is fishy? our family members are has aged and will not like to see the court.