What should I do if I get my China passport and go to visa country A, then sneak from country A to country B, and then return home?

You are an illegal immigrant in country B, and your status is illegal, so it is difficult to return to China through normal channels. Only when you get legal status in country B can you legally return to China from country B. If you can't get legal status in country B, you can only be kept in the dark until you are arrested, detained and repatriated by the authorities in country B and repatriated to China. The lightest thing to do is not to issue you a passport for several years.