As Adobe stopped development of Flash Professional's iPhone development tools after Apple said the App Store wouldn't accept apps created this way back in April – a decree Apple has only recently rescinded – Flash CS5's tools in this area are basic to say the least. Here's what you have to play with.
Flash CS5's iPhoneOS project preset is 320 x 480, the resolution of the iPhone 3G or 3GS. There there's currently no way to create apps at the iPhone 4's 640 x 960 Retina Display or the iPad's 768 x 1,024 screen. Apps you create will run on these devices – but won't look as good as native apps.
Flash-designed apps can't access the camera or microphone, but you can work with multi-touch gestures, geo-location information and the iPhone's accelerometer. You can also detect the screen orientation, save images to the Photo Library and cut and paste text to and from other apps. You can't run video directly within the app, and Flash video won't work at all. H.264 video can be viewed through opening the iPhone's built-in video player.
These features can be accessed using ActionScript 3 – code written in ActionScript 1 or 2 won't work. Note that the code you use is the same as for creating Flash 10.1 apps for Android devices (though different models will have some of none of the hardware features.
Hopefully, as Adobe has said that it now resumed development of iDevice output tools for Flash, the ability to create iPhone 4 and iPad apps – and access its full feature set aren't too far away.