It is not known as the how Saturn's atmosphere operates on a small scale is not fully understood. One thing that makes it seem unlikely, is that tornado development involves interation between a storm and a solid or liquid surface. There is no such surface on Saturn.
TORNADOES
While Saturn has some very intense storms, including some cyclones there is no real evidence of actual tornadoes on Saturn. However, our exploration od Saturn is limited, and it is unlikely that we could detect tornadoes or tornado-like vortices as, compared with other storms, they are much smaller and harder to detect.
Tornadoes can happen in any place that gets thunderstorms.
Tornadoes happen every year.
No. There are enormous, magnetically-driven vortices of plasma on the sun that have been compared to tornadoes. However, these are not true tornadoes as they operate on entirely different mechanics.
No. Mercury has essentially no atmosphere. There are no storms of any kind there.
Tornadoes happen in Miami for the same reason they happen anywhere else. See the related question for how tornadoes form in general.
Dk prolly melt lol
Tornadoes happen in Africa because of the mountains they have or because of the weather.
Tornadoes can happen in Ottawa. Canada does get tornadoes, though not as often as the U.S. due to its cooler climate.
The term you are looking for is tornado watch.
Tornadoes can happen anywhere in the world except cold areas like Antarctica and the north pole. Tornadoes are mostly common in United States.