Slum Rehabilitation Fraud

My father bought a house in a Chawl in the year 1998. Our Chawl was taken under the slum rehabilitation scheme in the year 2007 by Industrial Development Corporation (IDC) through builder saying that we are not patra under 1995. (XYZ) was the corporator at that time. In 2015 GR got passed for 2000 patra slums we got annex no. from IDC. 2015-20 till now the builder has given us 1.5 yrs rent only. In July 2019 IDC put the list of eligible slum people after this on 22nd august 2019 video lottery was conducted by IDC but the flat that was allotted, unknown people were staying. On 9th December 2019, my father wrote a letter of complaint against (XYZ), IDC, and builder to the MLA, CEO of IDC & DCP IDC police station. On 11th February 2020, MLA asked to collect the alternate accommodation possession letter and key of the flat on the next day. possession letter dated 30th Aug. 2019 & key was given by the (XYZ), but the alternate flat was not ready (under construction) till now it is not completed. What to do?