The phrase know something backwards and forwards means to understand something
completely and thoroughly. The phrase know something inside out has the same meaning.
If you have any quires regarding MS in foreign countries you can ask me. I know about MS backwards and forwards.
If you have a question about HTML tags, ask Mr.Ravi. He knows HTML inside out.
If you have a question about fundamentals in maths, ask our Mr. Shankar. He knows all the concepts in maths inside out.