Only with a telescope.
Yes, people were able to see the asteroid passing by earth. However, you would have needed a telescope, as you were not able to see it with the naked eye.
No, an asteroid cannot destroy earth, but a large enough asteroid can have devastating effects on the life on Earth
No, if the Earth was destroyed by an asteroid we would not be living today.
Yes, the asteroid belt starts properly after the orbit of Mars.
Yes, if the asteroid is captured by the Earth's gravitational pull.
Yes, as long as an asteroid is within visible distance of earth.
Probably not. I haven't seen any news about an asteroid about to strike Earth.
Theory suggests that it is a remnant of a large asteroid that struck the Earth
The Hayabusa ~ see related link below .
Some comets might also be invisible from Earth, we only see the big ones.
No.
Technically, if it hits the Earth it's not an "asteroid", it's a "meteorite". And yes, meteorites hit the Earth all the time.