Builder Forcing to sign Letter & giving back dated poss letter

I have purchased flat with above builder in Grace Square Project with proper registered agreement. The builder has given possession on June 2015 as per agreement. He also issued OC from Thane Municipal Corporation for the said project. Now my issues are as follows: 1) Though he has given possession and OC, he is not giving the possession letter. He is forcing us to sign "Consent Letter" and "No complaints in Future Letter". Without these two letter signed he is not giving us possession letter. 2) He has already taken sign on blank Possession Letter where he hasn’t mentioned any date on the letter. Now he is giving back dated possession letter. I have already demanded current date possession letter. As he had taken advance maintenance, the maintenance period shall start after giving the final possession letter. 3) The Builder has not provided sufficient parking and he has sold stilt parking to few members. As per the Supreme Court order, stilt parking is common area and cannot be sold or allotted by builder. Only society can allot the parking. I had emailed the builder demanding possession letter on 16th December 2015, he didn't reply. Then we sent a letter with sign of 11 members on 9th January 2016 stating other issues with above these. Still he told us that you won't get possession letter without consent letter signed. He threatened us with the name of local police. So we didn't go to police also. Now on 11 February 2016, I sent mail stating that you are forcing me to sign the consent letter and I will not sign the same and provide the possession letter without these sign. As he is not giving possession letter without consent letter sign, I signed the same on 13 February 2016. Now, he is giving me possession letter from 2 June 2015. I want the possession letter on current date. And my maintenance period will start from the date on which possession letter given to me. Please suggest any proper advice to get the possession letter from current date or how to deal with this issue.