Answer from cs61c-ew (Joo-Rak Son 16103505) for Question 1
C's loop statements (while, for, and do-while) are in fact not absolutely needed. All loops can be achieved through if and goto statements. For example,
while (!x) {
  a++;
}
can be done like this:
if (!x) {
  LOOP: a++
        if (!x)
        goto LOOP;
}
The same applies for "for" (which simply initializes and increments on top of while) and "do-while" (which only checks condition at the end).
I believe that the C designers included them for (1) it's easier to read and straight-forwarded to program, and (2) it reduces possibility of bugs because the code is simpler. In conclusion, convenience for the programmers and the fancy-ness of the code were of the main concern.