Question: How difficult must it have been for Mary to teach anything to Jesus? Wouldn’t he already know twenty ways to do whatever she asked?

Your question touches on one of the most intriguing aspects of Jesus: the fact that he was both fully human and fully divine. Admittedly, it’s hard to imagine how being fully God and fully man would work in practical terms, and it’s been a topic of great interest over the centuries. The Catechism says this:

The human soul that the Son of God assumed is endowed with a true human knowledge. As such, this knowledge could not in itself be unlimited: it was exercised in the historical conditions of his existence in space and time. This is why the Son of God could, when he became man, “increase in wisdom and in stature, and in favor with God and man.” (CCC 472)

In other words, even though Jesus was God, he was also a human being who grew up and learned as all humans do, from experience. We would hardly expect that the infant Jesus would be born with the ability to speak fluent Aramaic; that’s something that he learned as he grew. In the same vein, Mary must have helped him learn certain skills, like how to feed himself, how to dress himself, how to play, etc. When God takes the form of a baby, it’s to be understood that a baby needs a mom, and the Church has always honored Mary for filling that role.