Answer from cs61c-cj (Peter Lau 16539384) for Question 1
If only the datapath were pipeplined, the control logic for an instruction that entered the pipeline may change as it goes through the stages.  For example, instruction 1 enters the IF stage.  One cycle later, instruction 2 enters the IF stage with instruction 1 gets to the ID stage.  One more cycle later, instruction 3 is fetched and instruction 1 gets to the EX stage in which the ALU needs the proper control logic to know what operation to perform on the source registers.  However, with unpipelined controls, the processor will not have the correct control values for instruction 1 anymore.