How could it guarantee correct functioning with an outdated database?
It takes care of itself, because
the Eurocontrol-validated route will be wholly on current-AIRAC-cycle waypoints, as should the resulting plog
one should have a current DB in the GPS (OK I know many don't, and sometimes I forget to update, but then all bets are off)
As I say, if you have a current GPS DB, and you have a current validated route (not one developed a year ago), you should be able to simply spell every waypoint and it should work.
More likely, as with the XML flight plan format, the GNS needs coordinates together with the waypoint name. If those coordinates don't exactly match what it has in the database, you end up with a locked waypoint in the flight plan. While this works, it's a bit of a nuisance.
Hmmm... sounds likely. I recall this issue with loading flight plans into the old Skymap 2 
As I say, if you have a current GPS DB, and you have a current validated route (not one developed a year ago), you should be able to simply spell every waypoint and it should work.
The main advantage of VF according to their presentation is that you can use airways which the GNS do not know about. This obviously requires a correct and up to date database in VF.
If one just used waypoints, then it could be theoretically implemented without any database unless the GNS crossfill protocol requires coordinates which it most likely does.
This is how an .fpl file looks like that you upload to the GNS using a special card and the Garmin Flight Plan Migrator Kit:
That's a horrible system, which more or less guarantees periodic mismatches.
I suppose the software has to treat the floating point numbers as textual strings, not as floats, otherwise (short of using BCD floats) the chance of ending up with the same one millionths of a degree is just about zero.
I would assume it uses the Garmin coordinate format internally. The Flight Plan Migrator kits converts the XML to another representation which it writes onto the data card.
LAT/LON = Garmin format * 90 / (1 << 30);
I did some experiments with FPL files and a Garmin 695. When importing database waypoints all the 695 cares about is the name and the country code of the waypoint. It then searched the internal database and sources the coordinates there. Only if you have user waypoints in the FPL file it will use the coordinates. I wrote a gpx2fpl converter. And the difficult part is the country code. Most other formats do not contain this information. You have to use some sort of vector file with the FIR boundaries. If you do not all waypoints existing multiple times will be rejected. For example a "SL" NDB does exist about 10 times worldwide...
