In the past, I displayed disrespectful behavior and insulted both people and parents. However, they haven't shown anger or sought revenge. Should I interpret this as their forgiveness or do I have to approach each person individually to seek forgiveness?
Their not taking revenge or not showing anger does not mean that you did not wrong them. We must seek forgiveness from everyone whom we wronged. Without that, we will be accountable in the Day of Judgement which is the hardest day for the sinners.
Wassalam.