Which agreements in labor contracts between employers and foreigners are valid and which are not?

Take Shanghai as an example: According to Article 23 of the Provisions on the Administration of Foreigners' Employment in China, the working hours, rest, vacation, labor safety and health, and social insurance of foreigners employed in China are mandatory provisions of the State, and shall not be freely agreed upon by both parties. According to the judicial practice in Shanghai, the agreement on the content of the work, liability for breach of contract, calculation of economic compensation, etc. is not within the "forbidden zone" of the Provisions, and according to the principle of interpretation of "nothing explicitly prohibited by law is permitted", the two parties are free to agree on the content of the work.