This is the branch of handwriting analysis that determines whether or not two documents were written by the same individual. It is commonly, but incorrectly referred to as graphology.
Can you describe an individual's personality from examining handwriting?
There is some research to indicate that this is the case. That is a different field --- graphology.
The research tends to suggest that handedness can not be determined by examining handwriting. A rule of thumb, used by some handwriting analysts, that if an initial stroke starts on the right, and ends on the left, the writer is left handed.
No. That is an "apples and oranges" situation. Although there are some characteristics of writing that carry over between cursive and printing, you can not project from cursive how an individual's printing would look, and vice-versa.
The language that the documents are written in, are completely irrelevant. Most professional document examiners do not even read the document, concentrating instead on the details of how the script is written, what the ink is made from, etc.
Photocopies are not useful to determine the authenticity or otherwise of a document. Some examiners will make several photocopies of a document to highlight specific points when they examine the original document. Photocopied exemplars are more liable to be unauthentic, as non-photocopied ones.
Faxes have been described as the blurriest line between two points. As such, they are of no use at all, in determining authenticity. It should be pointed out that when the questioned document is a fax, or a photocopy, then those are the documents that need to be examined. And in those instances, those specific documents will be considered to be originals. However, even in those situations, examining the document that the fax or photocopy was created from, is usually required.