Cross-Platform Mobile App Design

I need a complete design plan for a new mobile application that will be released on both iOS and Android. From the first concept sketches through final, hand-off–ready screens, I want a coherent look, intuitive navigation, and clear documentation that developers can implement without guessing... (Budget: $15 - $25 USD, Jobs: Android, Figma, Graphic Design, iOS Development, iPhone, Mobile App Development, UI / User Interface, User Experience Research)