What is known as public technology in the patent law can undoubtedly be used for research and development. Regarding the significance of the conditions for granting patents in the field of patent law, it only suffices to be publicly known, and it does not necessarily require public use; or it refers to patents that are still within the validity period.
According to Article 63 of my country’s Patent Law, the use of relevant patents exclusively for scientific research and experiments will not be regarded as infringement of patent rights. However, in my country's current judicial practice, this provision is generally understood to mean that use is exclusively for scientific research and testing, which means use for the purpose of researching, verifying, and improving other people's patented technology, and the results of use are in the existing New technological achievements are produced on the basis of patented technology; on the contrary, if someone else's patent is used in the process of scientific research and experiment, the purpose is not to study and improve someone else's patented technology, and the result is not the development of new technology, it should be determined that for infringement.
Therefore, whether a patent that is still valid can be used by others for research and development should be determined based on the specific circumstances of each case.
For patents that have been applied for but have not yet been published, if, as you said, "the patented product is publicly sold or demonstrated in a public exhibition before the patent document is published (the audience can freely disassemble, Observation)" This situation may affect the legitimate rights and interests involved in patent authorization because the applicant has not yet obtained authorization for the technology and has not disclosed the patented technical solution at this time.
The protection of patent rights shall begin from the date of announcement of the authorization of the patent. However, for invention patents, the patent office will announce the patent plan eighteen months after the patent application date. At this time, it will still be quite some time before the patent is officially authorized. At this stage, if any unit or individual produces according to the published technical solution without authorization, it will inevitably affect the legitimate interests of the patentee after authorization. Therefore, Article 13 of the Patent Law stipulates that “after the application for an invention patent is published, the applicant may require the unit or individual who implements the invention to pay appropriate fees.” The protection of patent applications during this period is generally called "temporary protection". Once the application is granted a patent, it should be protected by a patent.
Since temporary protection is a special protection for an invention patent for a special period, its prerequisite is that the invention patent application is eventually granted patent rights. If the invention patent application is not authorized, it means that the application may be a well-known technology, or the applicant has given up the desire to patent protection for it. Therefore, any unit or individual who implements the technical solution cannot be considered as infringement or infringement. If it affects the applicant's patent rights, it cannot be said that special protection is granted to the applicant. Therefore, the filing of an application for temporary protection should be based on the grant of the invention patent right. Before the patent right is granted, the applicant cannot file an application for temporary protection.
It can be seen from the above that before the patent is granted, the patented technology is not unusable by others.