I think they are still testing
yes
July 16, 1945 was the first nuclear bomb test by the United States.
when France wanted to do what testing of a nuclear bombs on Moruroa island in the south pacific
France first nuclear weapon test was on February 13, 1960 and is believed to have a stockpile of around 300 operational nuclear warheads.
During World War 2 they set them off to test them, and to make Japan surrender unconditionally.
I'm think we can't theorize about the unverifiable but a fact is that a nuclear device creates a dense blast wind. In the other hand, many scientists believe that nuclear test in the deserts of the United States are the reason of the reapeted twisters attacks. In other words, nuclear bombs are linked to tornadoes already.
Yes, the US continued testing into the early 1990s performing somewhere around 10000 total tests.
No, they made their own. After their first test in 1949 (which was a copy of the US Fatman based on espionage) they designed them on their own also.
Between 1946 and 1958, Bikini Atoll was used to test nuclear bombs and the bikini swim wear was named after the islands.
In remote isolated places. Most testing (except for a few countries) is now done underground, to prevent fallout. The US has ceased all physical testing and uses only computer simulated tests.
The weight of a nuclear bomb depends on the bomb. Deliverable nuclear bombs have been built with weights as small as 50 pounds to as large as 30 tons. The first hydrogen bomb built (Ivy Mike test Sausage device) weighed 54 tons, but was never intended as a deliverable bomb (including the cryogenic equipment needed to keep its deuterium-tritium fusion fuel liquid the complete setup weighed 82 tons).
Desert is one of the places used to test nukes. It has chosen because they are unpopulated regions, radioactive waves are progressively atenuated as they go farther, and the observation of the bomb being detonated can be filmed in a safety tower. Other place to test is in the underground.