self-learning is described as, "questions about learning English by oneself."
Does it mean I should use it for every question I ask when I am learning English by myself? Or does the tag have a different meaning that it is not completely described in its tag wiki?
None of these questions seem to be about the subject "self learning."
self-learning appears to be a meta tag to label the authors learning technique (i.e. I'm a self learner). If that information is important, it should be included as part of the question text, not a tag. This tag should be removed from those questions.