Eight countries, Russia & US, each of which currently has a little over 5000 active weapons and parts from a similar number dismantled under treaty agreements; the other six countries none have more than a couple hundred active weapons. I do not have exact counts for any of the eight. Weapons yields are also unknown, and they can be more important than counts.
As of now, Afghanistan does not possess nuclear weapons.
You had better ask the Pentagon!
korea
absolutely
The U.S., at its peak state, had close to 32500 nuclear weapons (about the year 1965). They now have roughly 10000.
I don't believe anyone is supposed to have any kind of nuclear weapons due to the arms limitations treaties of the Cold War. I could be wrong, I'm not a big military official.
Nuclear weapons are right now the only barrier between WW3.
there are many harmful causes of nuclear weapons because whole hiroshima was destroyed of it
Many countries have nuclear weapons today including the United States. China, North Korea, South Korea, and Japan also have nuclear weapons.
The same as it is used now, for electricity production, plus nuclear weapons
zero
none