In any case, I would advise you to start with the latest LTS release (i.e., ROS 2 Humble Hawksbill). The rationale is that ROS 1 would reach EOL in about 2 years time, so even if you start developing algorithms in ROS 1, you would have to port them to ROS 2 in a couple years' time. Moreover, ROS 2 has a lot of fundamental design changes, which would require you to unlearn some of the ROS 1 concepts you would take time in mastering over a couple of weeks.

For simulation purposes, you have a plethora of options, although the Gazebo simulator is by far the most popular choice, owing to its easy integration into the ROS ecosystem.

As you mentioned you are also looking for learning resources, I will share two resources which helped me quite a lot: 1. The Robotics back-end : https://roboticsbackend.com/category/ros2/ 2. Articulated Robotics : https://articulatedrobotics.xyz/index.html Of course, you should also refer to the ROS 2 documentation as well, which is hosted at https://docs.ros.org/en/humble/index.html