Much of Christianity teaches “dispensationalism.” This school of thought teaches biblical history as a number of successive, but different, economies or administrations under Elohim, which it calls “dispensations.”
The logical reason for Noah to have known which animals were clean and which were unclean is for Noah to already have knowledge of Elohim’s Torah.
Genesis 5:1 conntains the first use of the word “book” in the Tanakh and gives us the genealogy of Adam. The first use of the word “book” in the Brit Hadasha is in Matthew 1:1. This is the record of the genealogy of Yeshua Messiah. This is an interesting correlation between the first Adam and the last Adam (1 Cor. 15:47).