Unfortunately, that just specifies which languages you prefer, regardless of what the original language is.
I speak Dutch and English, but have English set as my preferred language, because most of the time that multiple languages are available, that is the original language. However, sometimes I'll be visiting a Dutch site that has a (usually badly-)translated English version available, and I'd rather get the Dutch version.
You could probably also trick websites into serving the original language by setting a language they probably don't support (how many websites have a version available in Akkadian anyway?) but you'd need to pick something that the Google Translate widget found on many websites doesn't pick up and try to use.
No, because then it will probably serve it in the original language regardless of the languages I speak. If the original language is French, I'd still prefer to have it in English.
(To be clear, with how widespread English is, and how often Dutch sites are Dutch-only, this is a minor issue - having English, then Dutch as my preference is usually good enough.)
