Cross-Platform Guessing Game App (I can't reveal more)

I want to bring a simple yet addictive guessing game to both iOS and Android. Players will make their picks by tapping on screen options; no text entry or swipes are needed. Each week the set of items they must guess from changes, so I need an easy way to feed new data into the app and tweak the underlying values without issuing a full store update.

Gameplay & social layer
- A “global” leaderboard that updates automatically once a guess is locked in
- A light multiplayer mode so friends can compete in the same round and compare scores
- Weekly refresh of the guessing pool and its answers (I handle the content; you provide the mechanism)

Admin workflow
I’d like a small, secure dashboard—or any similarly straightforward method—where I can:
• Upload or edit the weekly dataset
• Toggle on/off individual elements
• Push the new round live instantly

Cross-platform build
I’m open to Flutter, React Native, Unity, or another toolkit that ships cleanly to the App Store and Google Play. Keep the codebase shared wherever possible so future tweaks stay efficient.

Deliverables
• Fully functional Android & iOS apps, store-ready
• Cloud-based or self-hosted backend that drives the leaderboard, multiplayer sessions, and weekly data
• Simple admin interface with authentication
• Source code and brief hand-off documentation

Please factor in any standard testing and deployment steps so I can publish without surprises.