Tax on relinquishment of inherited business - confused

My father was running a construction business and passed away an year ago. As legal heirs (mother + sister+myself) we relinquished our rights to my father's business partner so he could continue the business smoothly. My family (mother + sister) and I did a separate "family arrangement deed" relinquishing thier specific rights of the business to me so that they didnt have to be involved in long legal process and for sheer reason of convenience. Hence, I received the total consideration amount of X lacs to my account from the business partner upon reliquishing mine & family rights as legal heirs. I am planning to construct an extension of our current house for use by my family with the 50% of the consideration money in another 6 months. 1. How will this X amount be treated in the purview of Income Tax at my hand? 2. What are the different deductions/relief that I could get from IT? 3. Do I need to declare this amount after the construction of house or before only? 5. What are the steps I need to follow if I could not declare this amount in the Previous year returns? I have reached out to many local CA's and none have been able to provide me the correct guidance. So I seek some genuine help here.