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.
That depends on cache size too. Currently running Opera 37 beta (old UI) on (low memory) Android 4.4 the cache size is about 70MB and after that doesn't have a 'readable' location instead could be erased very fast.