The problem is that Turbo mode involves a proxy, which means it isn't actually secure.

Maybe the website they were getting it from no longer has it?

There is a keyboard shortcut to automatically add www. and .com to the address bar and attempt to go to that site; you must accidentally be hitting that shortcut - I believe it is Ctrl-Enter. If you are using the keyboard, make sure you release the modifier key(s) before pressing Enter.

Sorry, as a mod I try to look at all the (English) forums. Seems to me on a Mac you access it from the program icon, but not having one that's all I can say.

In this case, do it from the preview (on the right). But if you're worried you mistyped it, you should be pasting it to begin with.

Hold Shift (for new window) or Ctrl (for new tab) while clicking on Go to web address. No need for the extra menu items.

What version of Windows? On Windows 10, your profile would be at C:\Users\(your user name)\AppData\Roaming\Opera Software\Opera Stable\ - presume Windows is set to use English, some of the folder names are language dependent. And yes, you don't see any AppData folder - it is hidden. If you type it into the address bar of a file browser, it will show you the contents.

In a worst case scenario. you could delete the entire Opera Stable folder and Opera would recreate it the next time you ran the program - but you'd lose all your bookmarks, settings, history, and so on (at least, unless you use Sync; once you enable sync you'd get anything that it had saved back).

A better answer - if it works - is to only delete Preferences (your settings), but if some other file is damaged that may not be enough. Try this option first - if it doesn't help then you can back up your bookmarks and history then delete the entire folder, then (if Opera does work after that) see if you can restore your bookmarks and history.

Do you know whether it modified Opera, Flash, or just settings for either? You can of course reset your profile, or reinstalled Opera and/or Flash so I'm sure it can be fixed one way or the other.

There is a setting to remove the space above tabs in a maximized window - which is obviously already enabled on your system, as your window is maximized. So the actual issue is that maximized windows ignore this setting when returning from full screen mode.

Tabs during full screen are supposed to be higher (unless you've changed it).