In any case, you can apply, but not all of them can be authorized.
If no one has applied for the technical scheme proposed by himself, it means that the scheme is novel. However, to authorize, we must be creative and practical. Although some structures may not be carefully recorded in the prior art, it is obvious to the public to adopt this structure in order to solve a certain problem, so such technical solutions should not be authorized, otherwise everyone can apply for easy-to-think solutions, and as a result, the abuse of patent rights will hinder social production.
Because there are concepts of "novelty" and "creativity" when evaluating whether a patent should be authorized, their evaluation depends on the existing technology, which is a very broad abstract scope. It is not impossible for you and me to master all this clearly. The available technology is limited, and the definition of existing technology is worldwide, so it is generally necessary to search for the technical scheme you want to apply for before making a judgment.
However, due to the large number of applications, it takes a lot of manpower and material resources to retrieve each application, so there are patents-utility models without substantive examination authorization and patents-inventions after substantive examination.
Because the conditions for granting patent rights stipulate the concepts of "novelty" and "creativity", their evaluation depends on the retrieval results, and the retrieval scope cannot touch all the existing technologies, and the retrieval results vary from person to person, so even authorized patents may find evidence to prove that they are not "novelty" and "creativity", that is, they may be invalid.
Because general utility models do not undergo substantive examination, most of them can be authorized and get certificates.