MAVROS/C++ tutorial

[TPSetati]

Good day

I have a Sentinal drone and working on operating it with RS via MAVROS, but for starters I am working on getting the Gazebo simulator working first on a separate machine running Ubuntu 18.04 LTS and ROS1 Noetic.

Working through the MAVROS tutorial, I noticed 2 things:

1. The MAVROS Offboard Control C++ tutorial (https://docs.px4.io/main/en/ros/mavros_offboard_cpp.html) seems incomplete. Unlike the Python tutorial on the next page, the C++ tutorial does not explain the process of adding the launch file and adapting the CMakeLists.txt file to the project to get the simulator to run as depicted.

2. Something seems amiss when I try working through the tutorial on Sending a Custom Message from MAVROS to PX4 (https://docs.px4.io/main/en/ros/mavros_custom_messages.html). I add the custom lines to both common.xml files in the PX4-Autopilot/src/modules/mavlink/mavlink/message_definitions/v1.0 and workspace/src/mavlink/message_definitions/v1.0, but I notice that when I build the project, the custom lines in the PX4-Autopilot/src/modules/mavlink/mavlink/message_definitions/v1.0/common.xml are removed, and an error is generated with the mavlink_receiver.cpp (in PX4-Autopilot/src/modules/mavlink) where MAVLINK_MSG_ID_KEY_COMMAND is not declared in this scope.
   Could I be running the tutorial incorrectly?

[TPSetati]

Apologies. I actually have the simulator running on ROS1 Melodic.