A special issue is an edition devoted to a single theme, or to papers arising from a particular conference, rather than to the general mix of submissions that fills a regular issue. It is listed separately here so that readers looking for a themed collection can find it without searching through the regular archive.
Each entry above shows the volume and issue number together with the conference or theme it belongs to.
The difference is in the scope and the origin of the papers, not in the standard applied to them. A special issue is assembled around a theme; a regular issue is not. Everything else stays the same:
A paper published in a special issue is therefore cited in exactly the same way as any other paper in this journal.
A special issue is an edition of the journal devoted to a single theme, or to papers arising from a particular conference, rather than to the general mix of submissions in a regular issue.
Yes. The same peer review process applies to papers in a special issue as to papers in a regular issue.
Yes. Every article in a special issue receives a DOI, exactly as in a regular issue.
Yes. They are free to read and download, with no subscription and no registration.
Cite it exactly as you would any other article in this journal: authors, title, journal name, year, volume, issue, page range and DOI.