Hainan

Part one:

Correct information is that you can travel to Hainan as you wish and your wife will rely on a Hainan VOA. This VOA is existent and functional, but it is only recommended when an applicant is departing for Sanya or Haikou from Hong Kong. The reason is simple. Hong Kong airport staff is well trained and they are familiar with mainland China visa requirements. They will allow your wife to board the plane after she declares that she will rely on Hainan VOA. Any other or at least the largest majority of other airports that have international flights to Hainan would be reluctant to allow the boarding because they are used that people have visas obtained in advance or they are traveling on 30 day visa free access with invitation letters in their hands. This is an option that you have mentioned when you said "to contact with a Hainan travelling agency in advance for application". Anyway, you will not use this option.

So, when you arrive at check-in in Hong Kong, you will travel on a visa and your wife will declare that she will rely on Hainan VOA. After a short check, you will be both allowed to board the plane. Upon arrival in Sanya, your wife will apply for a Hainan VOA. The price for Norwegian citizens is 168 CNY. She can also bring a passport size photo to speed up the process.

Part two:

After she is granted a Hainan VOA, you will realize that this visa is valid for 30 day and the best detail is that with this visa it is allowed to travel to other parts of mainland China for up to 15 days. So, if you intend to stay in Hainan for 10 days, you can after that travel to some other part of mainland China and fly out from there to your home country. In reality, this is by far the most generous visa, but it seems that the Chinese authorities are slowly doing everything to phase it out in favor of 30 day visa free access. Of course, not within the next few months, but with the time, definitely.

Thanks a lot. It was very helpful, as it seems that the knowhow about this issue is quite limited, both by officials and travelling agencies. Even emplyees in Cathay ticket office didn't know the details...