iOS deployment target

Question

IF I set the deployment target for my app to iOS 4.2 when submitting to app store, will users with iOS 3.2 (or anything below 4.2) be able to download and install the app an

Answer 1

They won't be able to install and run the app (until they upgrade the OS on their device to that of the Deployment Target or above). But they might be able to buy and download the app using iTunes on their Mac or PC.

Answer 2

No, that's exactly what deployment version is about.

Best practice is to build against latest SDK version, with deployment version as low as possible. But that requires the discipline to do runtime checks and fallback implementations whenever using a API that wasn't there yet in the deployment version.