Itinerary Spain-Hong Kong-Guangzhou and back Guangzhou ( either from port/airport)-Hong Kong -Spain

That requires a visa because Hong Kong-Guangzhou-Hong Kong is a round-trip, and not a transit to a third country.

thanks and If I travel by plane to Guangzhou and then depart from any port in Guangdong area, would it be ok to get the free visa? Thanks again

You can return to Hong Kong via Macao without a visa. But you need a confirmed ticket for your journey to Macao in your hand when you check-in and also when you arrive in China. By the way, it is not a "free visa" because there is no visa involved at all.

Hi Rocio, Spain - Guangzhou - HK is eligible but you need to travel by ferry from Guangzhou to HK and you need to print the ferry ticket out and have it in hand when landing in Guangzhou.

Or you can make it this way: Fly from HK to Guangzhou, then from any place in Guangdong Province, like Guangzhou, Shenzhen, or Zhuhai to Macao by ferry, then continue back to HK by another ferry.

thank you so much!! and If I travel from Spain, transit (only to change planes) in Hong Kong and arrive to Shanghai and depart from Shanghai again transiting in Hong Kong would I qualify?
I am confused because I would be departing to a third country which is Spain, but due to flight connections need to transit in Hong Kong.
thanks

Hong Kong - Shanghai - Hong Kong does not qualify. It is not a transit to a third country. It doesn't matter where you go later. It is only the stops immediately before and immediately after China that are relevant.

Spain - Shanghai - Hong Kong - Shanghai - Spain qualifies (twice).
Spain - Hong Kong - Shanghai - Hong Kong - Spain does not qualify and requires a visa.

Thank you so basically I cannot use Hong Kong as transit to change planes if I want to avoid Visa?

You can do something like Spain-Paris-China-Amsterdam-Spain on Air France and KLM. That doesn't need a visa. Or combine Lufthansa with Swiss, etc. Many options.

ok thank you!