Sasuke cannot learn Limbo unless you want to suggest Madara and Hagoromo can learn Amenotejikara. Sasuke also did not copy Yomotsu Hirasaka from Kaguya, but he is using a different technique that can transverse dimensions, just like Kamui.
On the topic of whether or not Madara's Limbo dimension can be traveled to, in theory it can. Unlike SenseiSama however, I don't think so because all dimensions are linked and created by Kaguya, but simply because techniques like Kamui aren't bound by any amount of rules like that. Just as how Obito was able to return himself from the afterlife (still a dimension), it would not be completely insane think of visiting the dimension Limbo uses. The difficult/impossible part would be finding it's location, as even Obito had to sync with Yomotsu Hirasaka in order to find the location of Kaguya's dimensions. Limbo isn't traveled to or from so that's where the line is drawn.