Only one. Like many things, no two tornadoes are exactly alike.
Multiple tornadoes can form at the same time during a severe weather event, especially in outbreaks or supercell thunderstorms. The exact number of tornadoes that can form simultaneously can vary, but it is not uncommon for several tornadoes to be observed in the same area or region at once.
Yes, of course there can be two tornadoes at the same time.
In many cases the wind speeds of hurricanes and tornadoes fall into the same range, but tornadoes tend to have faster winds.
Tornadoes and twisters are the exact same thing.
Tornadoes form in the southern hemisphere for the same reason they form in the northern hemisphere. The mechanics are the same. See the related question for what causes tornadoes
Tornadoes do not have names. Australia has had many tornadoes, too many to list here.
A group of tornadoes produced by the same storm system withing a day or so is called a tornado outbreak. A series of tornadoes produced in succession by the same supercell is called a tornado family.
All tornadoes are produced by thunderstorms.
There were 934 tornadoes in the U.S. in 2002. Worldwide it is harder to determine as many countries do not keep records of tornadoes
There were 81 reports of tornadoes in Nebraska in 2011. However this only corresponds to only 55 actual tornadoes as sometimes the same tornado is reported more than once and some reports cannot be confirmed.
Worldwide figures are not available. In the U.S. a average of about 1500 tornadoes are reported each year of which 1200 to 1300 are confirmed. Some tornado reports are not confirmed as tornadoes, and sometimes there are multiple reports of the same tornado.
Yes, it is possible for tornadoes to occur during a blizzard. These tornadoes are known as "snow tornadoes" and typically form in the same way as traditional tornadoes, but are less common and generally weaker in intensity.