Hello Bhupinder,
You are right, you need to define handlers for your app. This is done by indicating the needed paths in the app.yaml file. Detailed related information and examples are provided on the "app.yaml Reference"
page, as well as the "How Requests are Handled"
page, or int the "Configuring your App with app.yaml"
document.
You are right about the 404 error code as well, it does mean that the address is not found. You can check at any time the meaning of these error codes on the "HTTP Status and Error Codes for JSON"
page.
This forum is meant for general discussion and voicing of opinions. For programming problems it is better to read dedicated forums such as stackoverflow, where programmers are active and ready to help.