Non acceptance of rent

I am staying in a room number 1 of a chawl consisting of 8 tenants. Few years back owner conveyed the said land to one builder. I have always paid rent of my premises on time and I have rent receipts of the same issues by the previous owner. After land was conveyed by the previous owner to the builder all the tenants started paying rent to the builder. Builder accepted rent for the period of 1 year after that he stopped accepting the rent. Every time we sent the cheque of our rent through register AD he returned the same. In 2017 he gave us the letter stating that currently we are not accepting the rent, once we start accepting it we will inform you. The said letter bears his rubber stamp. After that he held 2-3 meetings with all the tenants and said that he wants to redevelop the said property but non of the tenants agreed with the offer made by him. Now he has issued legal notice through his lawyer stating that non of the tenant came forward to tender monthly rent of their premises and the said letter given by him 2017 is a forged letter even the rubber stamp is false. He is asking us to produce proof of tenancy or else he will file eviction suit against us. So my question is 1) whether rent receipt is the valid proof of tenancy? 2) what steps can be taken if builder is not accepting the rent ? Can it be deposited in court? 2)