Weird how many people can get the wrong idea. there are several examples of this.
...that Ahmedabad mistake trying to do this quiz
I wish it were easy to just pack up a bag and travel the entire world for a few years. It wouldn't even need to be fancy -- I have no problem camping/couch-surfing/staying in hostels as long as it's reasonably safe and there's some vegetarian food. (Frankly, I think grand hotels can sometimes deprive travelers of a purer and truer experience of a place.) I did read about a couple who traveled and worked odd jobs to keep up the money to continue traveling... maybe one day.
Personally, I did find the regions distinctly unhelpful, although that's more because of the plethora of various asian ones. I understand why QM uses them though.
If we go off of citypopulation.de, here are a few more cities that I think are incorrect:
-Chongqing over Cairo, 28.8 million vs. 18.2 million
-Harbin over Hyderabad (and Ho Chi Minh), 10.2 million vs. 9.6 million
-Wuhan over Washington DC, 10.8 million vs. 8.6 million
Xiamen 2016 estimate; 3,920,000
Xi'an 2016 estimate; 8,832,100