Thanks for your reply! I have studied the RTW rules before booking this ticket, but just want to clarify some points that I do not understand.

As for my first question, the first HKG is currently a stopover. Are you saying that I cannot have two stopovers in HKG? The relevant rules I found are the following:

(e) Only one intercontinental departure and one intercontinental arrival permitted in each continent (with a few exceptions);
(f) Only one international departure and one international arrival from/to the country of origin permitted.

Neither forbids two stopovers in HKG. Am I missing something?

As for my second question, my main point is, am I only bounded by the max of 6 segments within the USA, as long as I do not travel the "transcontinental" flights more than once, right? That is, DEN-DFW-BOS-DFW-JFK is allowed?

Thank you very much!