Pagdi system / Vacant flat eviction concerns

Dear Sir My father owned pagdi system apartment in Mulund, Mumbai and after his demise in 1992 it was transferred to my mother. I am a NRI and my mother resides with me since 2016 as the condition of the house had deteriorated and was not in a living condition. The landlord was not willing to bear any cost to repair the same till now, however now he is supporting the repairs of the whole building by bearing 50% cost, since he has received notice from Municipality to either repair or redevelop. For all non-occupied apartments, the landlord has stopped issuing rent bills and receipts for any payment made since last 3 months, however we have continued to pay regular monthly rents by NEFT. Also we have paid 50% of the repair cost by chq however he has not issued receipt. The building is old and is due to go under redevelopment. Can the landlord send us eviction notice for not having any rent bill and no electricity usage for certain period / not staying there? Can the landlord just change the lock of the flat and possess it in our absence as it’s vacant and no belongings or furniture is there? What is the best solution to ensure they don’t possess the flat? My sister lives in Mumbai, if she lives there for a few days after the flat is reinstated will it resolve the issue or it is necessary my mother should stay there for sometime. Thank you