Need a flutter expert to convert existing native android app

The app source code is available in native, which we want to migrate in flutter.

Reguirements:

The app size should not exceed 20MB and be platform independent.

Developer should guide us how the other fantasy platforms are publishing the app in iOS and making it available for the users.

We need the complete app same to same with the existing one with all existing features. Partial app will not be useful at all for us , so you can send the code once the app is ready, no need for prior commit/push, but send the build during development for testing.

All the graphical contents and existing code will be provided once the app screens will be ready with the dummy contents.

Developer must have knowledge about native android code also , so that by studying the existing native code the backend APIs can be connected once the app screens will be ready.

Code safety is very much important, but it's all about pure trust.