Answer from cs61c-aq (Anjali Koppal 16454392) for Question 1
Everytime an instruction is decoded, it has new values for the control signals. if the control wasn't pipelined, these values would override the control signal values for the previous instruction. 
To save the control signal values for a particular instruction we need the control to be piped. as and when the instruction reaches a particular phase, the control signals for that phase are 'peeled off' and used.