1Your ratings are where you left themSigning in does not re-read anything or change a score. Everything you have rated and tagged is exactly as it was.
2A connected service stays connectedIf you connected one before, it is still connected. If a grant expired, the app says so and reconnecting is one click from settings. If you never connected anything, nothing here needed it.
3Trouble getting in?The help page names the specific failure rather than saying 'something went wrong', and there is a form on it that needs no account.