No, irregardless is not a real word. When someone says it, they mean to say regardless. The word doesn't even make sense because "ir" and "less" both mean not or without, so they cancel each other...
A base word is a word that has a prefix or suffix added to it (e.g fix, refix, fixed.) Fix would be the base word. A root word is a word that another word comes out of. "path" is the root word that...