Four second half goals as United take the lead but suffer from tired legs to Scottish opposition.
Man United have brought in three new players and others have progressed from younger sides.
Man United's youngsters open their UEFA Youth League campaign.
Goals either side of half-time for Man United saw the Reds win a second consecutive game in the U18 Premier League.
New signings Arnau Puigmal and Largie Ramazani are named.