I understand your worry, but nobody can help, I can only say that have a try in Spain, the approval of visa is up to the visa officer in Spain, he can refuse your application without any explaination, in fact, the visa application in a third country/region varies from place to place, maybe you can get it, but maybe your application will be refused.

yes, different place have different requirements.
Which type visa do you want to hold?
For F visa, we can send you business ivitation letter.
For tourist visa, you can apply for it by yourself.
I think you can apply for it in Hongkong. Maybe it is easier than in Spain. I am not sure,
i am a visa agent in beijing, specializing in the visa extension&conversion.
Questions about visa in China, you can tell me