Answer from cs61c-ep (Hao Wen Vivian Chong 15826235) for Question 2
if/else, switch, for, while, do, ?:, and most any logical operator can decide which operations get executed (such as <=, !, >=, ==, etc)

MIPS has beq, bne. slt, slti, sltu, and sltiu are also used to help make the decisions. The designers of MIPS might not have included more instructions for making decisions because that would have involved implementing it in hardware. It is simpler and more cost-effective to have just a few easy instructions hardwired onto the chip and then let software handle the rest.