Just wanted to know what id and handle mean in the context of the Qlik Engine API. How do I get values for those parameters and if I were to reload an app specifically say App B how would i go about doing that using the Qlik Engine API.
The id is set by the client, i.e you, and the engine will response with the same id to your request. That's how to link requests to responses.
Handles are pointers to objects on the server. The two standard ones, -1 is for the Global class and 1 for the App class. As you open new objects or create new objects the Engine will response with new handles as you keep opening / create objects.