Double header catching

Double header for Majors. Hypothetically a 12 year old goes 85 pitches in game one. Can he then catch in the 2nd game? If so, for how long?

And there has been some discrepancies in the explanation of pitching in double headers. Hypothetically a 12 year old pitches 40 in game one, can he pitch in game two? Is it based on a daily limit, or is there a game limit?

Any input is appreciated!