Are NDK features OS dependent? For example, if I have Gingerbread 2.3, can I only use NDK features for 2.3 and below, or can I take advantage of the latest fixes and features the NDK provides?
The main reason I'm asking is because it seems like the NDK is a completely different beast than the SDK, and due to the nature of C/C++ and the underlying internals of the OS should be cross version compatible.
Unfortunately it is as version-dependent as SDK. Each release of NDK bundles an ever-growing list of platforms. Typically, ndk-build chooses the platform according to android:targetSdkVersion as defined in AndroidManifest.XML.