Social Networking App Development Needed -- 2

I am ready to turn an idea for a new social-networking experience into a fully functioning mobile application. The core requirement is end-to-end mobile app development—from initial architecture through final submission to the app stores—so I am looking for someone who is comfortable owning the full build.

Platform. I have not locked myself into iOS or Android yet, so advise me on the best approach. If a single codebase with React Native, Flutter, or another cross-platform framework can keep maintenance lean, I am open to it; if two native builds make more sense for performance, make the case.

Scope at a glance
• Design and implement an intuitive social feed, user profiles, and real-time interaction (likes, comments, basic messaging).
• Set up secure authentication and a lightweight backend—Firebase or an equivalent cloud service is fine as long as it scales and keeps costs predictable.
• Provide clean, well-documented code so adding new features after launch is straightforward.
• Guide the app through testing and store submission, handling any compliance checks or resubmissions.

Acceptance criteria
1. An installable build (TestFlight, APK, or equivalent) that mirrors the agreed feature set without critical bugs.
2. Source code in a private repo with clear setup instructions.
3. A brief hand-off session—recorded or live—covering deployment steps and future update workflows.

If you have shipped social apps before and can point to live examples, tell me about the tech stack you chose and why it worked. I value clear communication and incremental milestones, so outline how you like to structure sprints and reviews.