Undue maintenance charges by builder

Hi, I would just like to brief you about the history of case, my father bought an under construction flat in a society, located at Greater Noida. We had paid all the sums required by builder by November 2016 and builder sent us a notice for fit out and registry of the same. However, due to my father accident we could not pay registry amount by March, 2017 and paid the same in June, 2017. For this delay, builder charged rs. 48,000 as holding charges which we got waived off by requesting the same. Please note that even paying registry money by June, 2017 the registry of flat was completed by builder in December, 2017. In the last demand letter, the builder has collected 1 year's maintenance charges in advance from us. When we went to take the possession of house in Jan 2018, after registry, we got to know that the modular kitchen and wooden work in rooms as promised by sales representative at the time of booking of flat was not being done. We instantly called that manager and asked them to do the same. He accepted his mistake and said that it will be done in a month. But it was just a fake promise, we followed up for more than one year and after 1.2 years of follow up, the builder completed the wooden work in Feb, 2019 and after that we took the possession. We did not take the possession before it as one of the clause of allotment agreement says, once possession taken, there will be no right on pending installations. After 2.5 years we got the possession of flat, but shocked to see that one years’ advance maintenance paid initially have been set up by builder and around Rs. 70,000 is pending as maintenance charge to be paid till date. I have raised the query with the builder and he said these wooden work was not written in your allotment letter and not part of the booking papers and hence, you are not allowed for waiver of maintenance charges. Yes it is true, that these fixtures were not written in allotment letter, however, at the time of signing up of the allotment agreement, we ask did ask the same from the sales person and he said that as all the flat owners above 17th floor will get these feature free and the present allotment letter is standard one and hence does not require to be included. But I have proofs of the same in the form of messages exchanged with Sales manager, emails and follow up messages etc. We are right now living in rent and due to this we were devoid from the rental income we would have earned. My query is whether (1) Our claim for waiver of maintenance charges are tenable in the eye of law though it is an oral contract but I have proofs as aforesaid and furthermore, builder has completed our promised wooden work which also signifies that it was promised else why he would do that? (2) Can builder charge maintenance charges before taking the possession of flat.? (3) Whether the above will be under the jurisdiction of RERA UP though OC, CC of the society are taken by the builder before the enactment of RERA Act or we need to file case under consumer forum? I request you to provide your learned advise on the above.