If I were to choose minimum API 4.1, does it mean the features in 4.0 will not be available to me if I use 4.1 as my minimum API? Or with each new API you get all the older features as well as the new ones?
Of course you get all the older features. The minimum means that features newer than that will not be available on all devices, and that you need to check the version before attempting to use them (or risk a crash).