The second problem is to reschedule and change visas. Rescheduling and changing the visa are different concepts. Rescheduling means changing the departure time separately. Since I can't travel because of something, let's take a rain check. Changing a visa refers to changing to another airline, which is generally difficult. If you book a ticket for Sichuan Airlines and want to change it to China Southern Airlines, it is basically impossible if it is a special ticket, but it is still possible if it is first class, so the rescheduling and change of the ticket are basically aimed at the airline you fly, and the futures are changed internally. Of course, first class is another matter.
If you reschedule, you may face the possibility of upgrading. After all, time is tight, so I can't buy discounted air tickets at that time. At this time, you have to make up the difference in the middle. Sometimes this difference is even greater than the loss of refund. It's up to you to choose whether to refund or reschedule.
I hope I can help you!