What planets have been landed on and whats the farthest anyone has gone in space?
Venus and Mars have been landed on. The furthest anyone has gone is the Moon.
Only our two nearest neighbours Venus and Mars have been landed on. Landing on another planet is technically challenging and many attempted landings have failed. Mars is the most explored of the planets.
Mercury could be landed on but the speeds involved and the proximity to the Sun are challenging. The Messenger probe orbited Mercury and then crashed into its surface which doesn't really count as a landing.
The outer planets being gas giants or ice giants don't have surfaces as such and so can't be landed on.
The only body that manned spacecraft has landed on is the Moon. The Moon is also the furthest into space that anybody has been. The furthest distance would have been in orbit over the far side of the Moon.