The rules do indeed seem to be perfectly clear only to people who have worked with them for years. For the rest of us, thank goodness there's FT.

To answer your questions, flights between continents do not count against the number you're allowed within the continent. And you may visit any city as many times as you have segments to burn with one exception: once you get back to the city from whence you started the whole thing (in your home continent, presumably) you're all done. Thus if you originate in Los Angeles, fly around the world, and want to keep the six North American segments "in the bank" for a few months for a later North American holiday, make sure your return home doesn't touch Los Angeles (or presumably any of the co-terminals in the area.)

A couple more things you should know: it appears true that if you buy your ticket on or after 15 April, your total trip will be limited to 20 segments. If you're aggressive and buy the extra two segments you're allowed, at the moment you'd be able to book at least 28 segments.

If you're new at this and haven't noticed, there can be a big price difference depending on where you start your trip.

Hope this helps.