Entirely on your device. No account, no cloud. Uninstalling deletes it.
You tap 2–3 meals, press "Hand it over", and give them the device. They see big picture panels and tap the one they want. The back button is disabled on that screen; returning to your view requires a long press on "hold to exit".
Not yet — data is device-local in this version. A family backup/transfer option is on the roadmap; it will be optional and clearly explained if it ships.
Edit the meal and retake or re-choose the photo. Photos are stored inside the app, so freeing space in your gallery does not affect them.
Premium purchases restore through Google Play / the App Store — use "Restore purchases" in settings. Meal data does not transfer in this version.
Email support@bollylabs.com with your device model, Android/iOS version, and what you were doing when the problem happened. Screenshots help a lot.