I must leave this country within 30 days before I enter the country. I'd like to book a plane ticket to Macau. Can I go abroad without flying?

What do you mean by "don't get off the plane after leaving the country"? Do you mean "don't get on the plane"?

If you book a plane ticket, change your boarding pass, then go through customs first, and then don't get on the plane, it is equivalent to not making a trip. The immigration authorities in China will handle the "cancellation procedures" for you, which means you haven't left the country, so you can't.

If you fly directly back to Macau, that's ok, provided you have a round-trip ticket, but why spend money on flying? So the tax on air tickets is non-refundable.

For multiple visas with a stay of 30 days, you must leave the country within 30 days at the longest, and you can go to Hong Kong and Macao.