How does the save/backup system work?

[Xantheo 0]

Please describe how character progress and related data (inventory, achievements, account bindings) are stored.
Clarify whether automatic server-side backups are performed and how frequently, whether progress can be rolled back in case of errors or data loss, and what procedures are in place for sync failures (for example, client-server desynchronization).
Please explain which data is stored locally on the device and which only on the server, and what protections/recovery measures exist for cases of account theft/compromise.

[Morendal 7]

1) All your progress is stored on the server!
2) Nothing is stored on your computer except the client!
3) Server backups occur every hour. 
4) There can be no server-side failures.
5) There can be no synchronization failures.  
6) You cannot be hacked in the game, as security is in place! 
7) We do not intervene in gameplay and will not restore items if you were hacked or scammed out of your own foolishness!** Choose strong passwords, do not share your account information with third parties, and do not download suspicious software.