Question about COS 306 Computer Architecture Study.com Final assignment

[exxxius]

It appears that, as of January 1st, this class will no longer be accepted by TESU. If you haven't finished it, finish it NOW. Some further helpful links I've found as I'm rushing to complete this class myself:

https://www.instructables.com/How-to-Bui...-Computer/
https://electronics.stackexchange.com/qu...-8-bit-cpu
https://www.youtube.com/c/BenEater/playlists

I'm still struggling with this assignment  :  Can't figure out the Control Unit, and now that I'm looking at the rubric, it says "Build the instruction selection unit using a multiplexer" which I think it's talking about the output of the operation blocks in the ALU and I did that, but the way it says "INSTRUCTION SELECTION UNIT" is confusing me as if they want a separate block for ISU just like they do for the control unit? 
I did the Final practice tests 16 times!!! Like 16 X 50 questions, and then last Saturday did the Final Exam and got 79 out of 100 (still pending proctor review). Worth to mention that literally not a single of the practice test questions were in the final exam!!!   Eventually I'm gonna transfer to WGU if I get enough points out of this assignment 
I'm drained and frustrated... Literally watched every single youtube video and tutorial and book on the internet but the way SDC assignment wants us to design the circuit is very different than all of the design processes I've seen from those tutorials and books! HELP!!!