Learn Farsi: زمانی که بادیگارد اینجا است، هیچ‌کس جز او این در اختصاصی را باز نمی‌کند. - When the bodyguard is here, nobody except him opens this exclusive door.

In Farsi, to express "only [someone] does [something]", we often use an exclusive restriction like جز (except) paired with a negative verb. Here, it is combined with هیچ‌کس to literally mean "nobody except him does not open". While English drops the negative in translation and just says "opens", Farsi requires the negative verb to complete this exclusive structure.

Does the double negative rule apply here because of هیچ‌کس?

Yes! Words like هیچ‌کس (nobody) and هیچ‌چیز (nothing) always require a negative verb in Farsi. So even if we removed the جز او part, you would still need the negative verb باز نمی‌کند to say "nobody opens". The word هیچ‌کس, the exception جز, and the negative verb all work together seamlessly here.

Can I use وقتی که instead of زمانی که to say "when"?

Absolutely. زمانی که (literally "the time that") and وقتی که are interchangeable when introducing a time clause. زمانی که just sounds slightly more formal or emphatic, which fits the context of bodyguards and exclusive doors perfectly.

Why does the object marker را come after اختصاصی instead of right after the noun در?