Answer to Question 1
The inner core is solid nickel and iron, the outer core molten iron and nickel, the mantle dense silicate rocks, the crust less dense rocks, the hydrosphere is water, the troposphere dense air, the stratosphere less dense air, the ozone layer is molecules, the ionosphere ionized gases, the magnetosphere just magnetic fields.
Answer to Question 2
Use the equation above Example 3 in More Precisely 1-2 to complete the calculation. 15 = 15/60/60 degrees = 1/240 degree (about 0.0042 degrees). Then the diameter = distance angular size / 57.3 degrees = 1.4 109 km 1/240 / 57.3 100,000 km.