Genesis 3:22:"Then the Lord God said, “See, the man has become like one of us, knowing good and evil".
Doesn't God say they started to have the knowledge of good & evil AFTER they ate the forbidden fruit & NOT before?
Yes, they knew good and evil immediately after their sin, that sin being the
first act of evil to be known, a sin that would instantly change their state of being, casting them out of fellowship with God. They had died. Before that they were innocent of the knowledge of evil, and therefore of good, since
everything they had experienced up to that time was good, God having
created everything good. But to oppose and disobey God is the most basic act of evil, opening the door to all other sins that would follow because, by that act, man had become his own "god" now, determining good and evil (morality) for himself. Sin would now flourish; evil would become common knowledge for man.
The Hebrew word used for knowledge here is most often used to denote experiential knowledge; to know a person carnally is one biblical example, or to know something directly, like a city, by actually traveling there.
Adam & Eve were given consciences-they did not lack a sense of right and wrong and would've been naturally and immediately repulsed by murder, for example, if it could happen in Eden, or a whole host of evils that have now become commonplace in our fallen world. But they had never
experienced these things; they had not known them; they were foreign. And the first and most basic law was commanded and enunciated directly by God so that they would've also already possessed a repulsion against disobedience, innately knowing that eating of the fruit would be wrong.
But the creature was given free will and he allowed the opinion and desire of creatures-themselves along with the serpent- to override
God's will, not yet recognizing the infinite difference between Himself and them, and of the absolute perfection of His wisdom. Presumably that would come later as they learned of the difference and of their absolute need for God-we don't know the fate of our first parents. But either way we're
all here to learn that same lesson so that, with the knowledge that parting ways with God only results in evils that we cannot overcome without Him ("Apart from Me you can do nothing", John 15:5), we may, with the help of revelation and grace, gain the wisdom to turn back to Him, the knowledge of good and evil having also played it's role in our "education".
And this explains why we're here, exiled from Eden into a place where, along with the good still inherent in creation, humankind has had to endure the evils of pain, suffering, sin, and death, the consequences of the ultimate evil that we also experience, being spiritually cut off and separated from our Creator. This is why it's so critical to regain the "knowledge of God", and this is exactly what Jesus came to reveal so that we may become reconciled with Him as we're willing. A teaching I'm familiar with says that, by his sin, Adam
preferred himself to God. That's the rebellious family tradition that we're here to learn the foolishness of. Human history and God's working in and through it make no sense if not for the fact that through it all He's meaning to patiently mold and draw humanity into the light, without force or determinism, as we become ready to accept it.