DotNap uses Apple's system alarms, which ring through Silent mode and Focus. If an alarm ever fails, first check that DotNap is allowed under Settings → Alarms. Starting a nap always requires alarm permission, so a nap that starts is a nap that can ring.
The one-time unlock is handled by the App Store. To restore it on a new device, open DotNap → the ⓘ button → Restore Purchases.
DotNap collects no data. The full policy lives at Privacy Policy.