The only clickable link on the app-checking screen was a button saying: "Uninstall Updates", as if instead of installing the full Opera program, I only installed updates to it. Puzzling...
At the moment only the desktop versions of Opera seem to support pass-phrase. So if you want to sync between desktop and mobile devices you will need to disable the use of a pass-phrase.
I've installed Opera Browser and Opera Mini (both for Android) and it seems that Opera Browser builtin adblocker doesn't work, even though it's already activated in Data Saving menu. Opera Mini adblocker, on the other hand, works normally.
Another weird thing: the adopted memory has a better performance than internal (random I/O included). I'm guessing that is true for almost all Chinese phones.