If I bring JAL from Sydney to Shanghai, there are some problems.

If you buy a JAL ticket and fly from Sydney to Osaka to transfer back to Shanghai, because your passport has an Australian visa, according to Japan's entry and exit regulations, you can get visa-free entry into Japan by showing your transfer ticket and Australian visa, and you can stay for up to 48 hours.

However, even if you have an Australian visa and a transfer boarding pass, the Japanese immigration officer still reserves the right to refuse you entry into Japan, that is, entry into Japan is not 100%, which requires you to be mentally prepared.

According to your description: in order to match the departure time of the flight, you need to stay at the airport for one night. If you can enter Japan smoothly, you can stay in airport hotel for one night; If you can't enter the country, you can also find an hourly room or hotel for transit passengers in the terminal, but the cost can be higher.

In addition, when purchasing JAL tickets, you can also entrust airlines to book hotels in osaka for you and entrust airlines to guarantee for you, so that when you fly from Sydney to osaka to go through the entry formalities in Japan, the probability of being rejected is almost zero. Of course, the premise is that the airline is willing to guarantee for you. If the airline promises to guarantee you, you will usually be required to provide good financial proof or pay a deposit to the airline.