I heard of but have no personal experience about such astral boundaries for beginning disciples. I have not had the interest to try to pursue investigations beyond our galaxy, since there is so little I understand even about my own planet!

It makes sense though that only individuals with a lot of development can have access to other galaxies in the internal planes, since each galaxy is governed by its own particular laws.

Just like learning to ride a bike, astral travel takes experimentation, trial, and error. However, to be successful one must be persistent and to keep practicing. This is how one develops competency in occult matters: consistency, discipline, and a lot of faith.