Question 1: What is the difference between an invalid diploma and
bogus diploma?  If somene receives a diploma from a prestigious
college without meeting degree and graduation requirements--required
courses are not taken and fake grades without work have been
assigned--is this diploma is bogus or invalid?

Question 2: What should this person do if the college has not
responded after this person returned the diploma?

Question 3: If the state regulatory agencies say "we do not have legal
authority over schools to enforce them to compensate students' losses
from an invalid diploma, what kind of attorney can help this person?
Or, is this an injury case, or consumer case?

Thanks a lot.

I doubt such would occur at a "prestigious" institution.  How did you
obtain the diploma?  Unless you are physically hurt, this is not an
"injury".

Maybe I don't understand the scenario.
Someone received a diploma undeservedly, either by fraud on his or her
part or because someone in the university "mistakenly" issued the
diploma (slipped a form with the person's name in the pile for the
dean and president to sign).  The person then returned the diploma.
Why, how should the university respond?  I can imagine that the
situation was quite embarassing and that any response could possibly
be misused to put the university in a bad light.
What is the injury?  The person had no right to the diploma.  If s/he
attended the university and paid tuition, s/he had access to the
courses.  Not earning and receiving a diploma is no grounds for
compensation.

Not to mention irisyoung-ga is expecting a bit much for 2 bucks.

As myoarin suggests, the operative word is "fraud" - as a matter of
law. I don't know that "bogus" or "invalid" would hold much sway.

If someone were issued a diploma due to fraud, and that fraud were
discoverable by the university in its normal course, and the
"graduate" were to use that diploma (and the supporting registrar's
records) to cause injury to another, there MAY be a cause of action
against the university.