I was certain that both дверь and двери can mean a single door – was I mistaken?
Yes, you’re right.
Okay, thanks. Then this sentence needs update of acceptable answers, then.
Not in Russian, as far as I know... in Ukrainian and Polish (and probably some other Slavic languages) there is no singular dver, only plural dveri. I don't think Russian is the same way... but I could be wrong.
It's grammatically plural, but «две́ри» can mean a single door (especially if it's a double-leaf door), so I believe "The door is far away" should be accepted too.
Yeah, too bad they haven't recognized двери as a synonym for дверь yet (despite reports).
It means the doors are not close by, are far away.
I hear the а in далеко pronounced as "ay"(as in English) instead of "ah" as it's usually pronounced.