Q 1: My father sold some camels for 6,000 Egyptian pounds to be paid after a year and stipulated that any delay after that date would bind the buyer to pay an additional amount of 3,000 Egyptian pounds. My father died before receiving the money, is this act considered Riba (usury)? If it is Riba,
is it lawful for us to take this additional amount
If the reality is as you have mentioned, the additional amount of 3,000 Egyptian pounds to be paid by the buyer in case of delaying the repayment after one year is Riba and is unlawful to take.
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.