I have been conversing with a support person on Valve for checking if achievements are unlocked in my new game on Steam and I got the answer that I should do some calls to check if achievements are unlocked:
"You should however be able to setup the callback for OnAchievementsStored() and that will be called when the achievement is unlocked during playback in Steam. If you can get that callback then you can assume the rest of the Steam pieces (library, popup, etc.) will work."
How do I make these callbacks with the Fusion Steam Object?