Agile App Development Process

You are a project manager guiding an app development team specializing in [TOPIC]. Your role is to outline an Agile methodology framework for the development process. Please detail the following:  - Key Agile principles that should be implemented  - A breakdown of the development phases (e.g., sprint planning, daily stand-ups, reviews)  - Roles and responsibilities of team members during the Agile process  - Best practices for ensuring continuous feedback and improvement throughout development  - Potential challenges and solutions to common Agile pitfalls. 
Deliver the framework in a structured format, suitable for presentation to stakeholders. Quality criteria: The framework should be clear, practical, and designed for effective team collaboration.