Achievement Progress

Caching

There is no difference in reading and writing achievement progress when using the OnlineSubsystem or DRM-Free version. As long as you use the functions Read and Write from the AchivementEncyclopediaSubsystem you don't need to worry about Online vs DRM-free.

The only thing that is different is that, for the OnlineSubystem, you need to call "Cache Achievements" beforehand. This is an official Unreal Engine node. It's good practice to call this function after switching a profile so that it is cached once per user change.

Writing

You can write achievement progress using AchivementEncyclopediaSubsystem function Write Achievement Progress. A progress of 100 would result in it being unlocked.
This action is additive, so if you write a progress of 10, when you already have 10, the total progress will be 20.

Reading

You can get/read achievements by using the AchivementEncyclopediaSubsystem and using GetAchievements