Tornadoes are least likely to form in association with a warm front, though it can happen.
Yes in every state. Not all states have violent tornadoes but all states have reported at least a few weak tornadoes, even Alaska and Hawaii.
Tornadoes can happen in any place that gets thunderstorms.
Tornadoes do not happen as frequently during winter or fall, with the lowest activity (at least in the U.S.) occurring in January and December. They mostly occur during the spring and summertime of April, May, and June.
Tornadoes happen least frequently in areas with stable atmospheric conditions, such as in polar regions and over large bodies of water like oceans. These regions typically lack the necessary ingredients for tornado formation, such as temperature contrasts and wind patterns.
Tornadoes happen in Miami for the same reason they happen anywhere else. See the related question for how tornadoes form in general.
Tornadoes can happen in Ottawa. Canada does get tornadoes, though not as often as the U.S. due to its cooler climate.
Tornadoes can happen anywhere in the world except cold areas like Antarctica and the north pole. Tornadoes are mostly common in United States.
Yes. Tornadoes, including some significant ones, can and do happen the the Philippines.
Tornadoes can happen anywhere - they're usually formed from severe thunderstorms.
Most tornadoes in the U.S. happen in spring and early summer.
Tornadoes happen in the summer every year.