What Musk is saying is that from a legal perspective, there are only three job titles/roles that must be filled in a corporation. Beyond that, they could literally have titles like "Grand Chief Space Wizard" and "Cheesy Toast" for various jobs and roles. They could call the role of General Counsel "Asshole in a Suit."
I think this quote is actually about a different point. The President, Secretary and Treasurer don't need any actual credentials for their role like a council needs a JD, but they have specific responsibility/liability in corporate legal structures.
The man is plainly over-reaching here, though perhaps it's an expression meant to bolster his public persona, and not an actual representation of his knowledge.
General counsel (at least in the Anglo-American context) means the senior legal advisor to an organization. As attorneys, they are required by law to have admission to the bar of the relevant jurisdiction, and to observe certain ethical standards and practices. This is not a made-up title and if it is that means there's a lawsuit for unauthorized practice of law that hasn't been filed yet.
Nope. I don’t know that you necessarily even need to have passed the bar exam in a given jurisdiction, much less have any kind of actual degree.
IMO, you’d be stupid to take a job like that if you didn’t have the degree and have passed one or more bar exams in the appropriate related jurisdiction(s), but I don’t know that it’s actually required.
You'd need to be licensed to perform the various legal duties one expects of general counsel, but general counsel is not a protected title and thus anyone within the company could be given the title. Musk is right on this one.