1957 USS Nautilus. First sub to travel beneath the North pole.
As regards military submarines meant as warships, the Russians built the submarines with the deepest diving capability, but U.S. submarines generally make less noise.
USA has the most nuclear submarines
Argentina had diesel-electric submarines while the British had nuclear-powered submarines.
A number of nuclear submarines sank, and the circumstances vary from accident to accident. Wikipedia has a list, and by going there and entering "List of sunken nuclear submarines" you can review that list.
Nuclear submarines are powered by a nuclear reactor and they are completely independent of air, so there is no need to surface frequently.
Nuclear power is used to generate electricity.
The US, Russia, Great Britain, France, China and (recently) India have nuclear submarines.
Yes, nuclear submarines generate nuclear power. There is a nuclear reactor on board (hence the tern nuclear submarine) which creates steam to drive the main engines to turn the screw(s).
Nuclear Energy
The PLA navy has more than 225,000 personnel and is thought to have as many as 70 submarines, 10 of them nuclear-powered
Plutonium can be used in nuclear reactors for nuclear propulsion of ships and submarines.
No - all submarines, be it nuclear or diesel-electric, use diesel fuel, either for primary engines (DE) or backup generator (nuclear).