Rent agreement.'

An agreement of rent was entered to lease out my commercial property for 11 months . After expiry of 11 months the tenant continued to stay and informed that he will enter into an agreement of rent for nine years (lockiing the rent period ) but inspite of repeated requests did not entered into written agreement. Now after 5 months he has sent notice for vacating the premises giving the reference of agreement which has already lapsed in oct 2017. I sent a reply that it was agreed to take premises on rent for 9 years so notice is not valid and if he wish to vacate premises he should pay 9 years rent and he never replied back. On his assurance of 9 years lock in period i incurred Rs 20 Lakh on increasing the power. Kindly give me an expert opinion whether an agreement which has already become invalid in oct 2017 giving reference of the same notice is served. Is this notice is valid. Kindly advise under law who is to pay stamp duty for registration of agreement I.e the Lessor or Lessee. What remedies are available to me. What I should write to him. Kindly advise at earliest. Mehra