Of course, you should contact the publisher and not the authors.
It depends on the type of publication: sometimes you have to pay a sum of money, in other cases it can be free. In any case it will always be necessary to mention the bibliographic source of the journal article.
You must apply quickly because the answer (from publisher) may take time.
It depends on the nature of the work you are working on. In many cases GOOGLE SCHOLAR helps with models of reference. You can type the title and pick up one of the models which can be Havard, Chicago, Vancouver, MLA or APA.
Since the publisher retains copyright, permission to use figures or tables has to be requested from the publisher. This must be indicated in the legends with reference and "with permission of (the publisher)". This is a useful reference for all questions of manuscript preparation: http://www.icmje.org/recommendations/.