Saving a file issue:
The beta version doesn't allow you to save a file to a specified location on the device yet. This is something I very much miss from the official release. I remember that Opera Mobile would prompt for write permission to external sdcard on Android 6. The beta is not concerned with write permissions to external sdcard because it only writes to the internal storage default Downloads folder.
BTW, thanks for the forward button on main toolbar. As mrninko has mentioned in a previous comment, the forward button appears active even when a page has no forward history. That needs to be fixed.
One more thing about button layout. I find that the user button bottom right is OK, but I find it uncomfortable that the tab buttons, offline, bookmarks, history, and downloads, are at the top, since you have to stretch the thumb to the top of the screen to make a selection, while all other typing happens at the bottom of the screen. Please add an option to place these tab buttons at the bottom, or simply place them there.