Reusable checklists for the routines you repeat.
Update to the latest version. A fix for this shipped in a recent release.
That is intended. Finishing a checklist resets it for next time, and an unfinished one resets on its own after 12 hours so yesterday's half-done list doesn't follow you into today.
Not directly — Task Loop has no account and stores everything on your device. Restoring a device backup to a new iPhone will bring your checklists with it.
Profile → Delete all my data. This is permanent; nothing is stored anywhere else, so it cannot be recovered.
So a location reminder can fire when the app is closed, which is the only moment it is useful. Your location is matched against your pinned places on the device and is never sent anywhere. See the privacy policy.
Email support and include your iOS version and what you were doing when it went wrong.