Don't chase the 6G certification until you can run a flawless 5G. Practice the on scrap pipe with a mirror. And remember: In pipe welding, your root pass determines your reputation.
Here is the breakdown of the 4 main pipe positions, from easiest to hardest.
These codes dictate the angle of the pipe, the direction of travel, and the orientation of the weld joint. Mastering these positions is a requirement for any pipe welder seeking certification.