Health certificates can generally be used across cities, and can be used across cities in the same province, and there is no need to re-apply.
The legal representative is only the person in charge. If you do not participate in the operation, you do not need to apply for a health certificate. For example, some foreign-funded companies need to apply for a license to engage in the import and export business of a certain food, but the legal representative is a foreigner, which only proves that he runs the company, but all the business is handled by China people. In this case, of course, the legal representative of this foreign country cannot apply for a health certificate.