Write to kshitij.koranne@icloud.com. Tell me your device and iOS or macOS version. I usually reply within two days.
Open Settings in the app, then tap Restore purchase. You need to be signed in with the Apple ID that bought it.
The daily puzzle is the same for everyone and changes at midnight on your device. A streak counts any local day on which you solve at least one puzzle.
Turn the daily reminder on in Settings and pick a time. If nothing arrives, check Notifications for the app in your device Settings.
Times reach the leaderboards only for puzzles solved without hints. Sign in to Game Center in your device Settings.
Games and stats live on your device. Deleting the app deletes them.