Is disobedience to God a sin? If so, how did eve disobey God before having the knowledge of good and evil?

The ability to sin is tied up with free will which is part of human nature, everybody therefore has this ability to choose or decide a course of action to take. Knowledge of good and evil as referred to the tree is not fact or information about moral laws. It refers to the desire or experience of evil as in the case of carnal knowledge with a woman means that you had sexual relations with her.