Cases and graded runs kept on the server under a code you hold — so they survive a cleared browser and turn up on any device the code is entered on. There is no account and no reset: the code cannot be recovered if it is lost, so write it down and keep it somewhere you will find it.
Your graded runs live on this device. Sending them to the vault puts a copy on the server under your code, so your progress is there when you open the app on your phone or iPad. This device stays the source of truth: a run still records with no signal, and nothing is lost if the vault cannot be reached.
Open a vault above and your graded runs can be mirrored to it, so your record follows you to your other devices.