SEGA has dropped support for these games and removed the IAPs, they are now offline and ad-free.

Crazy Taxi Classic Android iOS
Sonic CD Classic Android iOS
Sonic The Hedgehog 4 Ep. II Android iOS
Virtua Tennis Challenge Android iOS
Golden Axe Classics Android iOS
Streets of Rage Classic Android iOS
Streets of Rage Classic 2 Android iOS
Shining Force Classics Android iOS
Super Monkey Ball: Sakura Ed. Android iOS