As far as I know, the answer to your first question is "yes". (I haven't tested it myself but I have seen it used in apps to display a custom photo picker. E.g. in Camera+)
"An instance of ALAssetsLibrary provides access to the videos and photos that are under the control of the Photos application.
The library includes those that are in the Saved Photos album, those coming from iTunes, and those that were directly imported into the device. You use it to retrieve the list of all asset groups and to save images and videos into the Saved Photos album."
See documentation for ALAssetsLibrary: http://developer.apple.com/library/ios/#DOCUMENTATION/Assets...
"An instance of ALAssetsLibrary provides access to the videos and photos that are under the control of the Photos application.
The library includes those that are in the Saved Photos album, those coming from iTunes, and those that were directly imported into the device. You use it to retrieve the list of all asset groups and to save images and videos into the Saved Photos album."