Decree not done on a Compromise Petition against O.S.

Hello Sir, I have come across a residential project where I need assistance from legal experts. There was a land parcel that father partitioned among his 2 sons and 3 daughters. Younger son registered a case against his father in City Civil Court in the year 1991. Later in 2001 (father expired by this time), brothers and sisters compromised and went for a Compromise Petition. In the compromise petition, its detailed out like who will get what parcel of land and everyone have signed in all the sections of that petition. The younger daughter later sold her portion to prospective buyers outside her family. Now a builder is coming up with a residential project in this land. When we searched for the OS number online, its updated as Compromised and Disposed. We learnt that they did only compromise petition and not done a Decree against OS number. So my questions are: 1. Is Decree mandatory? 2. Without Decree, in future what are the issues that might arise with this scenario? 3. Is it advisable to proceed with this project? Thanks in Advance Shekar