Catholic teaching on the matter refers to the “fusion” of a human nature and divine nature as the “hypostatic union”. This union between human and divine is truly a “mystery of faith” that man cannot understand.
We know that God sent his only begotten Son to suffer and die as the Redeemer of mankind. WHY he did so by sending his Son through the conception of Him with Mary as his mother and the Holy Spirit as His “father” is not known. God could have easily sent his Son to earth in adult, human form and allowed his work to begin as an adult, but He obviously did not.
In studying this subject, I have concluded that God chose to allow the Redemption to take place using his Son aging as a normal human because it would be more “meaningful” than if Jesus just suddenly appeared, was killed, and then rose. We humans, I believe, are able to take away from the episode of Christ’s life and death much more with Christ having lived a full life as a child, boy, and man, than if Christ had just appeared as man.
Although the divine nature of Christ possessed the full body of knowledge (which is unlimited) as the two other persons of the triune Godhead - Father, Son, and Holy Spirit - I believe that the only “limitation” on Christ was the fact that he totally assumed human form. As such, he was subject to all of the calamaties that could befall any other man, with one caveat.
I mentioned this on another thread - the question was asked: as He was also human, was Christ capable of being “afflicted” with all of the things that go along with being human: colds, fever, stomach aches, headaches, insect bites, etc.? I believe the answer is yes, he was. But at the same time, because Christ’s presence on Earth served ONE primary purpose - the redemption of mankind - I believe that anything that might have detracted or “derailed” this purpose was “prevented” from occurring by God. For example, could Christ, while walking and meditating in the mountains, have slipped and fallen into a ravine and died of thirst or could a rock have loosened and fallen on top of him and crushed him to death? Practically and physically speaking - yes, these things COULD have happened. But, as I just said, I think that Christ enjoyed a unique “protection” from such calamaties that might have led to Christ not being able to fulfill his mission. So in this respect, I believe he enjoyed a protection unlike any other human.
But in the end, we know that Christ HAD to experience many things that a man would experience: love, sadness, crying, pain, suffering, and ultimately death.
I know it sounds like one is “punting on 3rd down”, but I do not believe it is incorrect to characterize the way in which the hypostatic union occurred as being a true “mystery of faith”. We simply have to throw up our hands on some matters and accept that the way in which God worked in some ways are simply too complicated or mysterious for us to fully comprehend.
I hope this makes sense.
P.S. I take issue with the person in the OP’s parish who said that Christ did not realize he was God’s son until he was baptized by John the Baptist. Christ fully knew he was God’s son BEFORE he was baptized by John the Baptist - we know this from reading scripture alone. Recall that when Jesus approached John to be baptized, John said that HE was the one who should be baptized by Jesus. But Jesus “corrected” John and said that it was proper that John should baptize Jesus, and so it was done.