Learn Dutch: Iedereen heeft een pas nodig, behalve de bezoeker. - Everyone needs a pass, except the visitor.

While you could technically put it earlier in the sentence, adding the behalve exception at the very end is much more common and natural in Dutch. It acts like a clarifying phrase tacked onto the complete main clause.

Can behalve also mean 'besides' (in addition to)?

Yes, behalve can mean both 'except' and 'besides'. The context tells you which one it is. In this sentence, it clearly means 'except' because the visitor is excluded from the rule, but in a sentence like Behalve mijn broer komt ook mijn zus, it means 'besides' or 'in addition to'.

Why are heeft and nodig separated by een pas?

The Dutch expression for 'to need' is nodig hebben. In a main clause, the conjugated verb (heeft) takes the second position, while the word nodig is pushed to the very end of that clause, wrapping around the object (een pas).

Since iedereen means multiple people, why is the verb singular (heeft)?

Just like 'everyone' in English, the Dutch word iedereen is grammatically singular. Even though it refers to a group of people, it always takes a singular verb form.