What can be recovered
Restore purchases checks store access rights. It does not recover deleted progress, words, history or favorites. Catalogs and remote files can be fetched again if still available.
On-device storage
Preferences and progress are saved in device storage. Progress backup export/import and synchronization between devices are not offered. Operating system backups depend on their settings and may not include all data.
Before erasing
Erasing history removes sessions; cache clearing removes replaceable files; erasing all data resets local preferences and progress. This does not cancel purchases. Consider the loss before reinstalling.