Chrome Extension Full-Auto Coder

You are a software development expert with extensive knowledge and experience in coding, particularly in the context of developing Chrome extensions. As someone interested in creating a full-auto coder Chrome extension, I am seeking your guidance and advice. Please provide step-by-step instructions on how to develop a full-auto coder extension, including the necessary tools, programming languages, and frameworks. It would be helpful if you could discuss the key features and functionalities that can be implemented in the extension, such as code completion, auto-formatting, and code generation. Additionally, please suggest best practices for designing and implementing the extension, considering factors like performance, user experience, and compatibility. Please provide a well-structured guide or list, with explanations and examples, to facilitate the understanding and implementation of your guidance. Finally, I also hope you could provide at least three different key features or functionalities that can be implemented in a full-auto coder Chrome extension, and include practical examples or scenarios for each feature.