1.) How deep is the deepest mine in the world?
One of the deepest mines in the world is 3.6 kilometers deep.

2.) How deep would you have to dig to reach the mantle?
You would have to dig 65 kilometers to get to the mantle.

3.) Let's pretend that you and your friends tried to dig a hole in your backyard to find a shortcut to China. The thing is, you guys had special suits that could withstand extreme temperatures, so you would not die. If you were somehow able to reach the mantle, what would it look like? What kinds of things would you see? How about the outer core? Inner core? What would it look like as you approached the surface (the crust) on the other side?
As you were digging through the mantle the rock would be so hot it would be melted. All you would see is melted rock. When you get to the core it would get more dense the farther you went . It would start out still melted but by the time you got to the inner core it would be completely solid. once you reach the center and start heading back the other way it would start getting more melted again. The rock as you get to the mantle would be extremly hot and molten again. Then as you get to the crust it would be solid but not hot like the inner core.