Can I apply for a patent after the product is developed?

You don't need to make a product to declare a patent. In China, there are three kinds of patents: invention patents, utility model patents and design patents. The content of patent examination for invention or utility model is whether the technical scheme that constitutes the patent conforms to practicality, novelty and creativity; The content of design patent examination is whether the design belongs to the existing design (similar to whether it conforms to novelty). The method of patent examination is the same all over the world. It is mainly to compare the patent contents in the documents you submitted with a large number of documents and literatures retrieved to see if they meet the above requirements. If it meets the requirements, a patent right can be granted, otherwise it cannot be granted.