Lying about God is not a sin? Satan is the father of lies. Sin began with Satan.
Sin entered the world from where?
From non-existence. Paul made the claim. He did not say it came from God in heaven. You think Paul would have claimed Satan instead of Adam brought sin into the world. I will stick with Paul on this.
Deception is a form of lying. Is there a verse that claims Satan lied to Eve? Is there a verse that claims Satan deceived Eve? Satan claims eating would not kill them, yet they did die physically and spiritually. People today still accept that lie. Both died physically. I accept that Satan deceived Eve. Satan did not know if they would die. Satan believed God would keep His word. Satan put all his bets on Eve and Adam.
4 And the serpent said unto the woman, Ye shall not surely die:
5 For God doth know that in the day ye eat thereof, then your eyes shall be opened, and ye shall be as gods, knowing good and evil.
Satan changed the death sentence to accusing God of withholding information. Both were lies based on Satan trusting God. Satan did not actually say God was withholding information. That was the implied deception.
"a tree to be desired to make one wise"
Eve accepted this lie. It would not give wisdom. It's very name was mysterious because it was the knowledge of good and evil. God even claimed God knew evil. God had already died as the Atonement for sin. God knew that Satan would decieve Eve, that Eve would convince Adam, and that Adam would disobey God, allowing sin to come into creation from nothing. It was in the very name of the tree itself.
Satan wanted to know what evil was as well. I don't know if he tried eating of tree, but if he did or had, what evil would he really know? One may conclude that Satan as the serpent had been eating, but gaining knowledge of evil in itself is not sin. The command was given to Adam and death would come only after Adam ate. One would have to speculate that Adam watched Eve die and change before him. All we were told is that Eve did eat, and she gave to Adam and he ate. Adam does not claim Eve deceived him.
"And the man said, The woman whom thou gavest to be with me, she gave me of the tree, and I did eat."
Seems he knew exactly what he did. We are never told the why. The result was:
"Then the eyes of both of them were opened, and they realized that they were naked. So they sewed fig leaves together to make themselves loincloths."
God did not lie. They died. Their eyes were opened. They saw they were now dead, and naked before God. All they could do about it was sow fig leaves together to hide their new condition.
If you claim Satan lied, you have to also claim they did actually physically die. Satan told Eve they would not die. If you claim they died much later, then Satan did not lie. Satan was not a liar until hundreds of years later when they did in fact leave their corruptible flesh. Only they did die and their soul left incorruptible bodies for corruptible bodies the second Adam ate. Coincidently that result made Satan a liar at that point. The point sin entered the world. Still sin was not a condition of Satan or the angels. It is the condition of Satan when human attributes are applied to his different physical endeavors to turn humanity against God. Satan cannot retain being a full angel and enjoy sin. Satan can only be the Adversary against Adam's flesh and blood as a spiritual being.
To be a sinner and a liar, Satan has to be something else rather than an angel. In the Garden he was the serpent, a physical being, with a physical body. Satan as the serpent, was a liar, after Adam disobeyed God and sin entered the world. He was a liar, because Adam and Eve physically and spiritually died. He claimed they would not. He did not lie, when he claimed they would be like God and know good and evil. If he told Eve knowing good and evil would make them wise, that was a lie. Wisdom was necessary to avoid living in sin and displeasing God. They started out being unwise in their new choice of clothing. Their first step in wisdom, was God chose what they would wear, proving that wisdom did not come from the fruit of the tree, as the serpent implied. Wisdom comes from God.
"Adonai, God, made garments of skin for Adam and his wife and clothed them."