Nice idea for a quiz. One thing: If you're going to insist on the full-length version of Sri Lanka's capital (i.e. not allow "Kotte" which at the moment you don't), then please spell it correctly - and allow all the correct variants of it (of which the answer in the quiz doesn't seem to be one). But honestly, "Kotte" is a reaonsable shorthand and it would probably be fair to allow that?
That is a common thing that has been said here on Jetpunk but it issomething has no back up in real facts. There have been plans about creating a mega city with Guangzhou as its core where it would merge with Shenzhen, Dongguan and Huizhou among others, but until that happens Shanghai is number one. I live in Shenzhen and in no way are we part of Guangzhou nor have I ever met a single person in this country who has ever reffered to Guangzhou as the biggest city in China or the world.