Is it now neccessary to create code for OS4?

Question

After the release of OS4, is app store is accepting applications for OS3? or OS3 applications are rejecting?

Answer 1

Apple is only accepting applications built using iPhone SDK 4, but that doesn't mean you can't create applications for < iOS 4 anymore. You should try building apps with Base SDK 4.0, so you can use iOS 4 techniques like multitasking, but set the Deployment Target to 3.0, so users on iOS 3 can still run your app. Of course you have to make sure you don't use iOS 4-only classes etc on iOS 3.