The AIR SDK is a free download available from the Adobe AIR SDK download page.
There is no concept of a shared runtime for Adobe AIR on iOS. The runtime is bundled with every application created for iOS, at the time of packaging.
The minimum namespace to use for AIR on iOS applications is 2.6.
You may find the details of this here.
Yes, you may use the 'Manage AIR SDK' option available in the Help menu for directly using an AIR SDK to package your application in Flash Professional CS6. For previous versions of Flash Pro, you need to overlay the AIR SDK using these steps.
Packaging and deployment
The various targets are listed here.
Yes. You can read about using the iOS Simulator to test and debug AIR applications here.
No. All applications deployed on device, even for testing purposes need to be signed with a valid certificate and provisioning profile, as described on this page.
No, since on iOS, applications use captive runtime, there is no way that the applications can use the features of a new AIR SDK without repackaging the application with the latest AIR SDK.
In this case, you need to specify the frameworks and libraries to be linked to in a platform descriptor file, as described here.
For such use cases, ADT has a switch -platformsdk which can point to the path to the new iOS SDK on the user's machine. Linking to new frameworks and libraries is described here.
To debug native extensions on iOS, you may use this link
Support for linking ANEs is available since Flash Builder 4.6 and Flash Professional CS 5.5.
You can find the details of using entitlements here.
Some ready-to-use native extensions can be found here.
The latest features for AIR can be found here.