Hanoi and back

Either of those routes are fine.

Still me, also, if my flight back to Hanoi does a stop-over in HK, does that count as A-B-C with A and B being different?

Thanks a lot, are we sure I am not required to be coming from my own country of nationality or from different region (like Europe)? Thank you!!!

Or if I take Hanoi-BJ with stop-over in HK and BJ-Hanoi with stop over in another place out of China?(it seems it cannot be stop-over in the same place as on the way there)? Still ok? Thx!!!

Three question - three answers:

1) Your itinerary Hanoi - Beijing - Hong Kong - Hanoi

Is eligible for 144 hour visa free transit and here you have

Vietnam (A) - mainland China (B) - Hong Kong (C)

Hong Kong is considered as a third country for visa free transit purposes. What is going on before Vietnam and after Hong Kong is definitely not of interest for Chinese immigration authorities.

2) You are not required to depart from your country of citizenship. This is absolutely not necessary and it was never a condition for anything. Your itinerary has just fulfill the A - B - C formula and your citizenship has to be from 53 eligible countries.

3) You can have an itinerary:

Hanoi - Hong Kong - Beijing - Hanoi
Hanoi - Hong Kong - Beijing - Bangkok - Hanoi
Hanoi - Hong Kong - Beijing - Macau - Hanoi

Or if you want to have a layover between Beijing and Hanoi, then you can skip Hong Kong entirely.

Anyway, you are definitely not allowed to have an itinerary:

Hanoi - Hong Kong - Beijing - Hong Kong - Hanoi

That clarifies my doubts. Thank you so much for taking the time to answer my questions!

perhaps one last question, if possible, when I book flights, do you know if better to select Hanoi - PEK - Hanoi and then choose combination of flights which fits the rule, or select "multiple destinations" flights? Thank you in advance!

Actually this answer is very important, could you come back to me? Thx!

If I were you I would use an opportunistic approach. I can see that Beijing is your main goal. So, you should try both of the mentioned options (methods) and see which one will offer you a more affordable ticket. In reality, both of the mentioned options are fine as long as they produce an eligible itinerary. Having all booking on one ticket or having several totally separate tickets, it is all acceptable under the visa free transit policy. Again, just look to spend as less as possible on the flights because you will have more to enjoy in your destination :)

Thanks, indeed that is it. However, my worry is that if I show a ticket Hanoi-BJ-Hanoi (a return ticket with same departing and return city, although with a stop in HK/Macao), immigration may say my stay in Beijing is not "transit". Do you understand my point? It is useless to spend less on tickets and then be denied entry stamp :D Can you let me know if you understand this?

my worry is in case HK is only stop-over on my ticket (so it is easy to see that HK is not the final destination of that ticket). I hope I was clear in exaplaining.

so with reference to my new request for confirmation below, if I have tickets as follows:
Hanoi - Macao - Beijing (one way, Macao is a stop-over)
AND
Beijing - HK - Hanoi (one way, HK is a stop-over)
is it eligible?
There is a difference between itinerary (just the list of cities you will reach during the trip) and ticket that you need to show when you go through immigration in Beijing.
Thx

You're over-thinking this and worrying too much! It doesn't matter where the final destination is, because almost everybody returns to where they started from eventually! Only two things matter: where the flight taking you to China takes off, and where the flight taking you out of China lands. As long as you can show a confirmed ticket for a flight from China landing in a third country, you will be fine. You obviously have to take that flight too, of course. It makes no difference if it's one ticket or two.