Full back requires very high football IQ. You have to be excellent at reading the pace of the game, when to drop, when to press, when to overlap, when to widen or narrow the pitch, when and how to play offside, when to play short inside or when to play long, as well as being able to read the winger you’re playing against, suss him out and nullify him.
If you can play full back, the chances you have the IQ to play CM, are very high.
Whether you have the physical attributes and ability on the ball are another matter. Luckily for this kid, he has both. The kid is a born CM.