Here are your answers:

1. 9

2. 3, Cloudtail, Bramblestar, and Berrynose

3. Reedwhisker

4. Cinderpelt

5. Bramblestar, Tawnypelt, Mothwing, Hawkfrost

6. Rusty

7. Cloudstar

8. Bristlepaw, Rootpaw, and Shadowpaw (yes, I know that they are not apprentices anymore, but I didn't want to spoil it for anyone who's not got that far)

9. Darktail

10. Mistyfoot

11. Bramblestar, Harestar, Mistystar, Leafstar, and Tigerstar

12. Flypaw

13. RiverClan, WindClan, and Thunderclan, vs. ShadowClan, and SkyClan

14. Jay's wing

15. Because she wanted to avenge her kits