Question 1

Why only five German cities?

Accepted Answer

Because the Bundesnetzagentur reserved a Drehbuchnummer block for exactly five: Berlin, Hamburg, Munich, Cologne and Frankfurt. Offering more cities would mean pairing a Stuttgart or Düsseldorf address with a phone number belonging to a different city — or with an unreserved number that might be someone's line. Restricting the list keeps every generated record internally consistent.

Question 2

Why is the house number after the street name?

Accepted Answer

That is standard German practice: Hauptstraße 12, not 12 Hauptstraße. Getting this backwards is one of the most common mistakes in software localised from English, and it is exactly the kind of thing an address form should be tested against.

Question 3

Are the Postleitzahlen real?

Accepted Answer

Yes, each is a genuine five-digit code for the city it appears with. The PLZ system is geographic, so the first digits narrow down the region — 10xxx is Berlin, 20xxx is Hamburg, 80xxx is Munich.