How may years the Tenant can stay after completion of Lease Deed

Dear Sir, My father and his brother together gave on rent to SBI by erecting the building and they registered lease deed for the tenure of 10 years commencing from 01.07.1997. In the lease deed it mentioned 15% increment for every 5 years upon mutual agreement. Where as in the year 2003 they created one white paper and forged my father signature, where as my father had a paralysis and he was notable to sign after year 2000. In that document they mentioned from 1.07.2002 to 1.07.2007 the rent enhancement 25% and mentioned as option to extend another two five years. Except initial lease deed after that we have not registered lease deed or Mutual consent letter for extension of Lease. From the year 2007 onward, i have spoken to the manager personally many times for eviction and he use to postpone they later we gave multiple written petitions. I was notable to close my father account where they are depositing because of his ill health and he was notable to sign due to paralysis. When i ask They were giving some reasons and not vacating. My father passed away in 2014, Recently i gave a Legal Notice to Chief Manager, Regional Manager and Zonal Manager through lawyer for eviction. Now my questions are 1. How many years the tenants can stay after completion lease deed or agreement? 2. Does Tenants have right to stay after completion of Lease deed? 3. Can i recover loss of rent,interest and penalty currently they are paying 12 years old rent 4. The building completely damaged and it has to demolished. Can i recover the building cost because it mentioned in the lease deed the tenants shall keep the premises in good order where as they are notable to maintain the building and it got damaged. 5. How long it will take normally in the court if i file a Civil suit on Bank. 6. I need this premises to start my own company, I am Software Engineer with 22 years of experience would like to leave the job sooner waiting for vacation of this building. Request you please clarify my above questions also guide me how to proceeed Thanks Prasanna .