Question: What is the furthest planet that has been visited and how long it take to be reached?

Chris Hackett answered on 22 Jun 2016:

furthest planet reached was Pluto (dwarf planet however), and the voyager spacecraft has gone even further and almost left the solar system. It will keep going and going on forever so it may reach another planet but we wont be able to contact it most likely. Furthest object humans have been to is the moon.