Some Problems of MFi Accessory Developing

Hi, I'm a MFi accessory developer. My accessory communicates with iPod/iPhone devices using iAP2. I encountered some problems when using iAP2 to access the media library and playback media items on devices. So could anyone help me with these problems? Any suggestion is appreciate!

Problems are described as following:

1. If I click previous track button in iTunesU, the current playing time will back to 0; but if I send hid command <Scan Previous Track> from accessory, there are no effect on device (this hid command is working correct on Music app and PodCast app);

2. If I set elapsed time with command <SetNowPlayingInformation>, there are no effect on PodCast app and iTunesU app (this command is working correct on Music app);

3. If I want playback some media items by sending message <PlayMediaLibraryItems>, it works on Music app and PodCast app but not iTunesU app;

4. If I change current playing items from music to audiobook in Music app, there are no playback queue list notification from device;

5. If I open a third party media app (such as QQ music) and send it to background then play other media items using Music app, the current playing time notification will carry a wrong value;

6. Music app doesn't notify the artwork transfer id sometimes.