If you make an app using Flash CS5, and the packager from October 2010, the app can run on the original iPhone as well as all of the more recent ones. If you make an app with Flash CS 5.5, the app cannot run on the original iPhone, or on the iPhone 3G. It can only run on iPhone 3GS and the more recent models (iPhone 4, iPad, iPad 2, iPod Touch 3rd and 4th generation). So, if you don't mind making the app only work for the iPhone 3GS and later, then you should get CS5.5 and use that. If you want the app to work on the older iPhones, then you have to stick with CS5, and use the old packager. If you do that, you won't be able to have the multitasking feature.
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