Answer from cs61c-cj (Peter Lau 16539384) for Question 1
No, two different MIPS instructions will be unique.  They cannot have the same bit pattern because the computer cannot make a decision and resolve any ambiguity in two identical MIPS instructions.  Also, the RISC philosophy aims to keep the simple case fast, so if all instructions were given a unique bit pattern, the computer can easily execute it without having to compare or extract information to decide what to do.