Do the rulings that apply to biological children apply to adopted children? Is saddening the adoptive mother considered disobedience (عقوق) even though she is not the biological mother? Does the prayer of an adopted daughter for her adoptive father have the same effect as the prayer of biological children after the father's death?

The rights of parents are immense, and Allah Almighty has associated their rights with His own in the Holy Quran. However, this does not preclude showing kindness to those who have shown kindness to you, such as your mother's maternal aunt and her husband. They deserve kindness through pleasant words, good companionship, and supplication for them. It is not a condition that supplication be only for parents to be accepted, for supplication for any Muslim in their absence is answered, so how much more so for those who have shown you kindness. And be assured that honoring parents does not cease with their death; supplicate for them and honor their friends and relatives. And know that the mother's maternal aunt has a great right to honor and kindness.