What the Big Mac index reveals about a global currency beef

1.What is the Big Mac index actually designed to reveal?

2.The article calls Trump the world's most "strident" critic of cheap Asian currencies. Strident means:

3.A Big Mac costs $6.22 in America. You convert $6.22 into Mexican pesos and it buys two Big Macs in Mexico. According to the index's logic, the peso is:

4.Why does the article open with Le Grand K, the platinum cylinder near Paris?

5.The article says China's yuan could become less undervalued even if its exchange rate never moves. How?