How to know all commands for each mode that work on sitl? also how to locate code logic behind each command on the arducopter's code so as to modify it for simulation purposes?

I am working on a project to modify some functionalities on the traditional copters and render them as tailsitters. I am facing problem to figure out how to interrelate code and its physical context wrt the vehicle’s movement . I would like to figure out how to relate SITL commands to their corresponding code logic in the Copter’s codebase for each mode.