When Christ was tempted, Satan was not sure if Christ was the Son of God. "If you are the Son of God"
This is mentioned in the Mystical City of God.
And the unclean spirits, when they saw him, fell down before him: and they cried, saying: Thou art the Son of God.
Mark ch 1
And there was in their synagogue a man with an unclean spirit; and he cried out, Saying: What have we to do with thee, Jesus of Nazareth? art thou come to destroy us? I know who thou art, the Holy One of God. And Jesus threatened him, saying: Speak no more, and go out of the man.
When satan tempted Jesus, it was only to his human nature and will that he could appeal, even though he knew Jesus also to be God.