Is it illegal to pretend to be a courier and go to the property to check San Xiao's information?

Break the law. Without legal procedures, others have no right to inquire, which involves personal information, which is protected. Article 253-1 Crime of infringing citizens' personal information selling or providing citizens' personal information to others in violation of relevant state regulations. If the circumstances are serious, he shall be sentenced to fixed-term imprisonment of not more than three years or criminal detention, and shall also or only be fined. If the circumstances are especially serious, he shall be sentenced to fixed-term imprisonment of not less than three years but not more than seven years and shall also be fined.