For Question 8, think about the different addressing modes used by different classes of instructions (i.e. Data Movement, Operate, Control). Operate instructions use different addressing modes than Data Movement instructions. For example, the ADD instruction uses the register mode. One or both of its operands are in registers.
No. You should only use R1 and R2, if you need to store any values.
You cannot solve this problem until we cover the LC-3b state machine in class. Therefore, you are not responsible for this problem. It will be a problem in the second problem set.