[walruslover66]

For part 2, where you have to find which board would BINGO last, I took the approach of going backwards.

Set all numbers in all boards are "marked"
Going through the number drawings backwards, unmark numbers on every board with that number
Each time a number is removed, evaluate that board for ANY BINGO
As soon as you reach a board with NO BINGOs on it, that is the final board to be completed

This makes sense with the restriction that every number is called exactly once. But part of me is thinking there's another restriction for this solution to work, but I can't place my finger on it. Anyone else know?

FWIW, my solution works, so whatever hidden assumption I'm struggling to think of is being fulfilled.