#5 Can a DCNote be forged ?

Depends what you mean by "forged".

The origin of a DCNote is a digital vector-based file, which can be output in any size or resolution. that file is never released, except as physical object or low/medium resolution pixel-based file.
Those physical objects can, of course, be copied, but the loss of quality would be obvious, since they are very fine - a uniform 5% grey DCNote would have about 350 000 tiny dots - about the same as the number of people in Iceland - it can not be copied by analogue means (photographing or scanning).

The low/medium resolution pixel-based files can be duplicated indefinitely - that is fine - if released, they are released for that purpose, to the DCNote owners or Station Masters.

If you mean producing an entirely new image that pretends to be a DCNote -- no, that is easily checked/verified against our public log on:
›DeepCheque.Org/Recognize