Would humanity's destiny have been different if Iblis had not disobeyed his Lord and prostrated to Adam? And does the created being possess the ability to disobey the Creator, or is it the will of the Creator?

Adam's expulsion from Paradise was not due to Iblis's refusal to prostrate, but rather because Adam ate from the forbidden tree. This act of eating was caused by Iblis's temptation. It is narrated in the Hadith that Adam said, "Did anything expel you from Paradise except the sin of your father Adam?" Some scholars believe that if Adam had not eaten from the tree, we would have remained in Paradise, and they cite Moses' words to Adam: "You are our father; you disappointed us and expelled us from Paradise."

As for Iblis's ability to disobey the Creator, Allah Almighty enabled Iblis and all creation with the capacity for both obedience and disobedience as a test and trial. So, whoever disobeys Allah among them disobeys by their own choice and will. Iblis had the choice to prostrate or to refuse, and he chose to refuse. His disobedience occurred with Allah's knowledge, will, and creation, for Allah Almighty is not disobeyed by coercion; rather, He enabled them with this choice.