The game should be in your program files>Steam>Steamapps>common>Il-2 Cliffs Of Dover folder.All the files are there.There is also a 1C folder in your documents folder that holds some game files.
Steam only updates official patches.1.05 is the last official patch.There have been some betas(1.0
and a couple of release candidates(1.09 and 1.10).Betas and RCs have to manually d/led and manually installed.
All you need is the last RC2(1.10) if you want.