Voyager 2 did a fly-by August 25, 1989 .
August 25th of the year 1989CE, at 09:23UTC, Voyager 2achieved closest approach to Triton. No spacecraft has landed there yet.
No spacecraft has visited all the planets.
Pluto will be visited by the spacecraft New Horizon in 2015
As of 2011, only one spacecraft has passed relatively close to Neptune. The Voyager 2 probe visited Neptune in 1989, having previously passed Jupiter, Saturn, and Uranus. Voyager 2 took the first close-up photos of the Neptunian moon Triton, and discovered five inner moons: Naiad, Thalassa, Despina, Galatea and Proteus.
voyager 2
Voyager 2 is the only spacecraft to have currently visited both.
yes
Yes
There are many planets in our solar system that have not been visited by a spacecraft. As of now, the planet Uranus has not been visited by any spacecraft.
Depends on whether you say Pluto is a planet or not. If you say it isn't, then there are no planets that haven't been visited by a spacecraft. If you say it is, then there is one that hasn't been visited yet, but one is on the way.
none
Apollo 17