Sometimes our on-line catalog doesn't contain every product made at any particular time. If it is labeled and sold as 18 AWG, then it must be correct. It is soft drawn (SD).
I don't know. It comes as 1 wire stranded.
Please contact a local electrician. The above advice is based upon the current edition of the National Electric Code (NEC). Free access to the latest version of the NEC is available online at www.nfpa.org/freeaccess. The NEC and local building codes regulate the types of wire and cable that can be used in specific electrical applications, as well as the manner of installation. Check your local building codes before you start any wiring and cable electrical project and be sure to obtain required permits. When your work is complete, always have it inspected for compliance with local codes to ensure that it has been safely installed.
Yes this offered in a 500 ft roll.
Yes, it is bare copper.