No. Not once outside of Hiroshima and Nagasaki. They have been used for scare tactics though.

No. The only combat use ever of nuclear weapons was on Hiroshima and Nagasaki.

I'll add to that, as well. No. The reason being that no one wanted to be responsible for the end of the world. The closest we came was the Cuban missile crisis in 1962 when the soviets placed ICBMs in Cuba, capable of blasting any major us city. Luckily, they came to an agreement before shots were fired, but honestly no leader wants to be responsible for the end of the world as we know it.