I would think Jesus knew of his previous human existence growing up. When he was 12 and his parents, after searching, found him back at the Temple; he definitely knew something then. I would think his parents would mention something so significant.
The baptism was when he received the holy spirit and with it the power to perform miracles and forgive sin. The clouds parting and such was simply confirmation from God for the onlookers. There were people constantly waiting there to see who John (the baptizer) kept talking about.
He already knew who he was. When fully, who knows.