Who is the prophet talking about here? It is about Tyre, but, he mentions the prince of Tyre first ( many scholars believe this is the city and the human king) and then turns to the king of Tyre ( same scholars believe this is Satan, just as in Daniel the angel told Daniel that he would have been there sooner but the prince of Persia resisted him, suggesting a spiritual being is ruling over the human king). If this is Satan being spoken to by the prophet then it tells us he was a guardian cherub (possibly guarding at the throne of GOD) and tells of his glory and beauty and wisdom. It also tells of his pride and then fall from grace. My question then is this... If Satan was in the garden of Eden as a cherub, and was perfect (as the scripture says)
In chapter 28, we find the judgment of the prince of Tyre and Sidon. The prophecy looks beyond the local ruler to the one behind the kingdoms of the world-Satan.
In verse #2 we have the viceregent of Satan..."Because thine heart is lifted up and thou hast said.....I am God". This is a picture of the anti-Christ. The prince of Tyre says......"I sit in the seat of God, in the midst of seas".
I believe that this prince of Tyre represents the religious ruler aspect of the Antichrist.
Now......the serpent was just the form that the devil chose to take--at that time a beautiful and innocent-looking creature. Satan knew that God's angels would have warned Adam of the enemy (remember that there had been war in Heaven before Satan had been cast down to this earth), and that if he had appeared as a noble angel, Adam and Eve would have been on guard and wary of him.
Rev. 12:9........
"And the great dragon was cast out, that old serpent, called the Devil, and Satan, which deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him."
The Bible is clear that Satan had sinned already prior to his disguised appearance in the Garden of Eden.
As already partially quoted in the question:
1 John 3:8..........
"He that committeth sin is of the devil
; for the devil sinneth from the beginning. For this purpose the Son of God was manifested, that he might destroy the works of the devil. "
Jesus also alluded to this in John 8:44......
"Ye are of your father the devil, and the lusts of your father ye will do. He was a murderer from the beginning, and abode not in the truth, because there is no truth in him. When he speaketh a lie, he speaketh of his own: for he is a liar, and the father of it."
The fact that the devil "sinneth from the beginning," is "a murderer from the beginning," and is "the father" of lies implies he was the first to commit these sins.
So then, Yes, Satan, also called the Devil, the great dragon, and "that old serpent," was the first to sin, sinning before being cast out of heaven and entering the Garden of Eden where he next tempted Adam and Eve to sin.