The unlock progress of a particular achievement can be retrieved using ovr_Achievements_GetAllProgress(). It can be used to display the progress of each achievement in your game. See the following link for more information.
The unique string that you use to reference the achievement in your app, as specified in the developer dashboard. It can be retrieved using ovr_AchievementDefinition_GetName().
unsigned long long ovr_AchievementProgress_GetUnlockTime