What did the Lord Jesus Christ know, and when did He know it? At what point in His earthly existence did He become self aware of His deity, and the saving purpose for which He came into the world?
There are no definitive Biblical answers to these questions. "Great is the mystery of godliness; God was manifest in the flesh" (I Timothy 3:16). Some might say that as God, our Savior knew from the moment of conception in Mary's womb that He was who He was, and that He had come to redeem us from our sins. I recently heard a very respected friend affirm this. This may be true, and I am comfortable with the possibility and understand its logic.
There are Biblical clues that might lead us to believe otherwise, however. Luke's Gospel tells us that the Lord Jesus "increased in wisdom and stature, and in favor with God and man" (Luke 2:52). Such growth indicates that omniscience (perfect knowledge) was not a characteristic of our Lord during His earthly sojourn as a human being. He did not relinquish His deity, of course, but enrobing Himself in humanity for our sakes apparently brought limitations necessary for His identification with us. My view is that this may have involved the necessity of discovering His nature and being, and subsequent growth in knowledge thereafter. Through the Scriptures, the Holy Spirit, and the teaching of Jewish religious leaders, the Lord Jesus may have come to know who He was, and then grew in the wisdom and knowledge of being God, "manifest in the flesh."
The Bible records that Joseph and his family went to Jerusalem every year for the feast of the Passover (Luke 2:42). During this time, the primary subject of the doctors' teaching in the temple would have been God's deliverance of Israel from the yoke of Egyptian bondage through the blood sacrifices of the Passover lambs. The young Jesus would have been exposed to such teaching year by year, and this could have played a role in His coming to understand Himself and His mission. It is interesting that Scripture mentions the annual visits to Jerusalem and the Passover, and the fact that at 12 years old, our Lord's awareness of "My Father's business" is revealed in context of His time in the temple (Luke 2:49).
Most importantly, the truth shines before us that the sacrifice of the Lord Jesus for us was far greater than we can ever imagine. Becoming human, with its inherent limitations, after eternally having been solely Divine, with its inherent boundlessness of being, nature, and way - what can such condescension involve and imply? This is especially overwhelming if the Lord Jesus had to discover and grow in His self knowledge, because becoming human meant that He temporarily sacrificed the very awareness of who and what He is as God the Son.
"Great is the mystery..." Whatever the truth may be in this holy consideration, our Savior embraced for our sakes a sacrifice far greater than time or eternity will ever tell. We are loved beyond every understanding of the concept we can contemplate. We are the source of joys in the heart of the Father, the Son, and the Holy Spirit that were birthed in sorrows forever untold. Our Lord who is God will also forever be a man, and He will forever point a nail-scarred Hand in our direction to proclaim in grace and mercy, "Behold I and the children which God hath given Me" (Hebrews 2:13). Yes, our Lord considers His church as a gift of the Father to Him. But it was a gift that came by way of a sacrifice far greater than time or eternity will ever tell. A cross of shame, agony, forsakenness, and death bears witness to the price of our redemption, and to a dark and terrible hour when the Savior cried out into the darkness of bewilderment and a broken heart...
"My God, My God, why hast Thou forsaken Me?"