No, we don't know of any black holes close enough to get to.
Nobody has ever visited a black hole. The nearest known black hole is many light years away. Much to far away for us to reach it.
You're question is badly worded, but sure, in theory humans could reach black holes.
Technically, you can't "see" a black hole, since no light can escape from it, therefore the light cannot reach your eyes.
yes, when you fall near to the black hole due to it's immense gravity you will be spaghettified and you will die before you reach the singularity
depending on the size, stellar black hole , yes. Supermassive black holes, no, once you reach the singulaity you are outside of the universe, and you vanish, forever, you don't exist anymore.
Things falling into a black hole are ripped apart by tidal force, become a stream of their constituent atoms. These atoms are further shredded by the time they reach the singularity, and the mass of what is sucked in is added to the mass of the black hole.
If you enter a black hole, no matter what the speed, you will be sucked into the center of the black hole, and utterly destroyed.
In what way? It's reach? It's size? It's energy output?
Yes! It is because time is relative, and so the process of getting sucked into a Black Hole will be long enough for you to live your life before your body begins to disintegrate. In fact, even right now you are in the process of getting sucked into a Black Hole at the center of our galaxy. But it will take millions and millions of years for you to reach the point where you enter the Hole. It purely depends on the intensity of the gravitational pull of the Black Hole. If it has infinite gravity, then it will take you infinite amount of time to reach it.
No known person has been through a black hole. The nearest known stable (stellar mass) black hole is too far away for us to reach with our current technology, and an encounter with one would almost certainly be fatal.
In fact you would die outside a black hole. At least in the case of a stellar-mass black hole, the tidal forces, i.e. difference in gravity between your head and your feet, would be strong enough to tear you apart before you reach the event horizon.
Since black holes have a huge mass, objects are attracted to it. Once you reach a point called the Event Horizon, good luck getting out. YOU WILL NOT. We do not know much about death by black holes at this time, but some scientists believe that once you reach a certain point, you will be ripped to a strand of atoms. I do not recommend going near a black hole.