Can the company issue a return guarantee and resign after the visa comes down?

This is just a proof of your income source, indicating that the company will reserve a position for you until xx. During this period, the company will not pay you. This certificate corresponds to your visa requirements and has legal effect on whether you return to the company or recognize your reserved position in xx. It is not the company's guarantee that you must return to China on xx. In fact, there is no need for your company to do this, which proves that some writing is redundant. Just prove that you are an on-the-job employee of the company, and your position and income are accompanied by your salary table. You can do without running water. Just bring your salary card and bank account when you get a visa. What the visa officer wants to know is whether you have a source of income and how much. It is used to judge whether your income can support your life in this country.

As for your visa, where will you work and live in the future? Has nothing to do with this proof.