Rest of country huh?
Well I don't know about the rest, but for one we in Izhevsk also have this подъезд meaning. And I didn't ever heared anyone using "Парадное" for the same thing. Some people on this board used to search for dialects of Russian alot.. perhaps they should note this obvious difference of St-Pete Russian Dialect

About the metal doors, now.. We also have lots of them (2VM: I didn't say 'all', right?), both on the "подъезд"s and the flats inside. Sometimes there are even more of them - one metal door behind which there is a hall to two or three flats, each of which may also have the metal door.. but I've only seen one such appartment building.

The purpose of flat's reinforced doors is obviously to protect from the flat robbery, and the fact that lots of people installed them once tells something about the actual need for them. I for one may say that once some junkies actually tried to break in to my flat.. it seems that they've been so drunk that have forgot that the person they tried to find here have long been moved... Well maybe something's wrong with the city part I live in But hey, it's still Russia, right? I also heard stories about how the flat robbers removed even the metal doors using the lift, but maybe this is the urban myth

The purpose of "подъезд" doors here primarily is to protect not as much from the thieves/terrorists, but from the youngsters and the бомжи who are used to use the "подъезд"s as the drinking place and the toilet. As such things tends to happen at night when doors are usually closed, the подъезд doors are actually doing their job.

Well now, the picture is unplausible to foreigners I guess.. But this is the reality. What can I say? Maybe - don't come to Izhevsk? Instead go to the Peterburg with парадноеs and no metal doors on them because every lies which unfortunately are truths in Izhevsks, are only just a lies there, according to the VM of course. That's to the discussion on the difference between Moscow/St-Pete and the rest of the Russia. Because most foreigners probably will only see the former rather than latter, maybe they really better off hearing to VM rather than people like me.

P.S. Any English grammar corrections are appreciated