What you could do, is to first watch this Course with 2.90 and after that, watch the 4.2 Version of the Course (CORE) with 4.2.
Texturing is quite complicated and watching it twice, explained in different ways and also in different Blender Versions will be really helpful.
That being said, the 2.90 Course is by Jonathan Lampel, who has had a lot of experience teaching Blender and the new Version by Ewa Wierbik-Ziąbka is one of her first Courses, and also made under great time pressure.
