Sterling tied it at 85 in overtime and put Alcorn State up for good with 57 seconds left. The Braves made 7 of 8 foul shots to seal the win.
Mosby scored Alcorn State's last four points in regulation with a pair of free throws and a layup with 39 seconds left to knot it at 82. After Mississippi State called timeout, Mosby stole the ball from Nate Nahimy. Sterling missed his 3 attempt as time expired to force overtime.
Mosby and Sterling combined to shoot 20 of 21 from the free-throw line, Maurice Howard chipped in 14 points and Yalen Reed added 10 points and grabbed eight rebounds for the Braves (8-17, 4-8 Southwestern Athletic).
Mannion, who recently reclassified and is ESPN's No.11 overall player in the class of 2019, chose Arizona over Marquette.
He'll fit in with Sean Miller's plans for a faster tempo on offense.
The cream of the crop of American high school basketball will congregate in Colorado Springs from Oct. 5-7, as USA Basketball unveils its newly expanded Junior National Team minicamp in collaboration with the NBA, NCAA and NBPA.