2.10) I found a note marked "SPECIMEN" with a serial number of all zeros, what is it?

  Specimen notes are printed for banks and law enforcement as a reference
to identify notes.  Most countries have specimen notes where the word
"specimen" is printed in the local language.  Sometimes the notes are
perforated with the word.

  Specimen notes are often worth more than notes for circulation, but
there are exceptions, especially when lots of specimen notes are created
for collectors.  Specimen notes aren't legal tender so they don't
have a face value.