First, the right of first use is not given to the patent applicant, but to the infringement suspect. It is only used in the process of judging infringement, and has nothing to do with priority. For example, on May 1 day, Party A applied for a TV patent and was authorized. On April 30th, Party B had installed a production line to produce the same TV set, or before that, Party B had been producing this TV set, so it didn't expand the production scale, which was not an infringement. As for "continue to manufacture and use within the original scope", there is no specific provision, which needs specific analysis. Generally speaking, the production equipment is ready and should be considered ready.
Second, priority is for patent applicants, but we should pay attention to the difference between priority date and patent application date. The filing date is a fundamental starting date of all deadlines in the process of patent application processing, which is simply not detailed; The priority date is mainly used as the starting date for examiners to retrieve documents when examining patent applications, which is not after the filing date of patent applications. In your example, A filed a patent application in China with the filing date of 20 10 1, which enjoys the priority date of 20 1 kloc-0/,and the examiner will only search before1. At the same time, as far as the validity of the application is concerned, your domestic overdue application will not affect Party D's application, and if all of them have the authorization conditions, because Party D's application date is earlier (for example, September 30th), then Party D will be authorized and your application will be rejected.