Usually not required. However, if they plan to stay here longer than 6 months, you need to apply for an permit of extension and medical examination is mandatory. And, if the visitor is older than 70 years, the medical exam will be required no matter how long he/she will stay.

     Usually not required.

     Visa would be issued in same day by walking in apply, but probablly more than one month by mailing apply. While you must have all the required documents prepared and sent them into the embassy without being asked for extra materials. This will speed up your application dramatically. The luck ones can get the visa 2nd day after the documents were handed in. So the most important is to gather all required documents as complete as possible and send thme to the embassy.