6 month grace period

On April,2013 my agreement was done and I got possession on Feb,2016.As per MOM with builder I will be entitled to get compensation Rs 12000 as a rent from builder if they delayed the possession date which was mentioned on agreement(30 month from the agreement).Later on builder changed their statement and said the compensation amount will be adjusted with maintenance amount which was supposed to paid by me(Rs 44,100) to builder and they also mentioned only those buyers will be eligible who got delayed possession as per agreement(After 30 months). Two years back I got maintenance amount due reminder mail (After adjusting delayed compensation Rs 36000= Rs 12000X3) from builder side which was Rs 8160.I immediately paid that amount .In between many times they put notice board mentioning maintenance amount defaulters names they never mentioned my name, as per their record I paid all the pending maintenance amount. Recently they stopped my housekeeping services(Picking up garbage) without any notification or communication and asking for the Rs 36000 more by saying they didn’t calculate grace period previously now they are calculating grace period and asking full maintenance amount .Point to be mentioned here they never mentioned 6 month grace period in the agreement only mentioned "The promoter shall be entitled to reasonable extension of time giving delivery of flat on the aforesaid date, if the completion of the building is delayed on account of . 1. Non-availability of steel,cement,other building material, water or electricity supply.2. War, Civil commotion or act of God . My Quarries are: 1. Is there any law where by default builder can get “ 6 month “grace period after completing the 30 month deadline? 2. Can builder stop housekeeping service without any notice or intimation? 3. What action can be taken from my side against builder? Although builder hasn’t sent any communication regarding pending amount. 4. Can I sent a legal notice to builder? 5. What is the procedure and cost to sent a legal notice? Builder details: Builder name: Khemchand Bhojwani(Pyramid Developers) Project name: The Nook,Pune RERA NO: P52100004015 Sir It would be really great help for me if you guide me on the same. Thanks and Regards Laltu Dey