Learn English – “I have not had an answer” – what is the real meaning

It is very common to read "be upset" as be meaning "to be bothered" [about something or with someone].

John was upset about the news that his dog was missing.

I hear it used to mean "to be angry" sometimes:

John is upset with you because he thinks you let his dog out.

However, being upset with someone is a very mild form of anger. If John were really annoyed the terms "angry" or "pissed off" would be used. Moreover, I would not consider this to be a translation of 慌てた (awateta) or, in present tense, 慌てる (awateru), which I think would be better construed as meaning to be confused or disconcerted about something. 慌てふためく (awatafutameku) seems a better candidate for "flustered" or "panicked" — that kind of upset.

Moreover, you can be upset about things that you didn't just learn about. You can be upset about things that happen over time.

Marvin has been upset ever since he started that new diet.

Upset comes from the term meaning "knocked over":

In reaching for a fork, Joe upset his champagne glass and spilled its contents all over the table.

Yes, has been around means 'has been in existence'. The OED gives only ‘to have gained much experience in the world’ but in practice the expression is used rather more widely, if only in informal contexts.