The regular expressions and denote the same language.
Any language consisting of all but finitely many strings over some alphabet is necessarily regular.
If A is any regular language, then is always an infinite language. If A is regular and B is a finite language, then is always regular. If A is regular and B is an infinite language, then cannot be a regular language. It is possible for a context-free language to be also a regular language. State the pumping lemma for regular languages and use it to show that the language or is not regular.