Part 2:
a. I want to limit current to at most 30mA. Per the Forward Current vs Forward Voltage graph on page 2, the forward voltage of the Red LED at 30mA is 1.9V. We're using the 5V supply, so the resistor would theoretically have to be (5V - 1.9V) / .03A = 103.3 Ohms.
b. The voltage in part a is a minimum resistance to ensure a maximum of 30mA through the LED.
c. The resistance range of the potentiometer (between the wiper and one side) is theoretically 10K Ohms.
Part 3:
a. For this circuit, the order does not matter.
Part 4:
a. (9V - 1.9V)/.03A = 236.66 Ohms.