Answer from cs61c-es (Meng Chang Bruce Lin 16075852) for Question 1
MIPS instructions generally fall into R, I, or J types. Where J type is specific for jump instruction. For R and I types, certain instructions might have similar bit patterns. In another word, in R and I types, some fields might look the same depending on how instrucions are implemented. However, the overall bit pattern should distinct from one and another. If two instruction are the same in 32 bits representation, that mean a memory block hold 2 instruction, which should not be possible.