Toomek
Sorry to hear the news, i know how you feel, i failed at stage 3 last time but have one last go at it this year. Contact HR soon and get your feedback as to what you need to improve on for next time. They should give you a detailed response on each criteria and think about your responses for next year. I took some comfort that not that many people get to stage 3 which in itself is a great achievement. If you put the same effort in next year you should pass stage 1 and 2 again.
Good luck for next year and i would strongly suggest that you try again. HR actually told me its worth me applying again, which is nice to hear !!!