

Can I use Visa Free Transit during my visit in HK for one day?
I’m an US citizen and have an Asia trip planned originating from US to each of the following cities by air and the duration of stay in each city is about 6 days.
The travel itinerary is as follows:-
US-OSAKA-HK-HANOI-SHENZHENG-TAIPEI-PVG-OSAKA-US
I understand that I could use 2 - 240 hours visa free transit during my bottom half of my trip from HANOI onward if I’m correct. Please confirm.
Me second question I would like to find out is:-
While I’m in HK ( arriving on a Saturday and departing 6 days later on Friday ), I would like to go into Shenzheng by train if possible or through Lo Wu on Monday for one day returning the same day. I departs 4 days later on Saturday for Hanoi. Can I use the visa free transit policy to go into Shenzheng for one day and not departing for Hanoi till several days later after returning from Shenzheng?? Which visa free transit should I get since my departure from HK IS NOT IMMEDIATE??
Thanks for your expertise and advice for assistance. Look forward to hearing back from you.