Answer from cs61c-af (Annie Tran 16811592) for Question 1
I think this question is a little vague.
I don't understand exactly what you are asking me but my answer to this question is:

1. varibles are not directly translated into assembly language they have to be stored and load through MIPS functions.

2. When retriving or storing a value in an array, the 
index has to be multiplied by 4 and added to the base
address. 

3. when trying to add/subtract more than 3 operands
assembly language has to translate the one line c code to multiples instructions in MIPS.

Their purpose is to allow the programmer to write shorter and clearier codes.