2.2 is the version number of the BN OS (aka "ROM") which itself is based on Android v4.0.3 which is quite dated (see
http://en.wikipedia.org/wiki/Android_version_history). Now that the HD/HD+ have been discontinued it's unlikely that BN will release further updates to their OSs.
Android apps or app updates that are developed for recent versions of Android OS more often than not would not be backward compatible with older Android OS versions.
It's worth noting that "Rooting" the stock ROM does not update its base Android OS version to a newer one. The only way to get a newer Android version for the HD/HD+ is to use 3rd-party custom ROMs such as CyanogenMod -- current CM11 builds are based on Android v4.4.4.
Occasionally I have run into some apps on Google Playstore that would refuse to install/update on my HD+ which is running CM11 -- but the very same apps or app updates from an alternate source (such as 1MobileMarket) would install/update just fine.