1. Screenshot is from desktop, but I had the same view in Mobile. What happened was: I primarily use desktop, and opened up the mobile app for the first time in a while. I opened this file on Mobile, and noticed that everything showed as untitled, and it also had created a duplicate file because of a sync issue. I then tried to open on desktop, but I saw the same thing - two identical files, both showing all tasks as untitled.
2. They became untitled in both places.
3. I'm pretty sure it showed as untitled as soon as I opened it, although I believe I tried to edit it after that to see if it would help
4. It's whatever the latest was when I posted - I think 10.16.7.