Got this from Indya.com
Week 9-11: From Week 9 onwards, we have only the Champion's league left (In an ideal situation, this could be a mix of the original Champions and the Challengers). Thus, on every Friday all remaining Champions perform solo's. The Jury marks this performance. This day's score is carried forward to the next day and it has 25% weightage in the overall score. The next day, i.e. the Saturday episode, the Champion's perform Duets with an Industry playback singer. The jury yet again marks them on this performance (the weightage of these marks are another 25 %) and simultaneously, the voting lines are opened for the audience. The audience voting has a 50 % weightage in the overall results. Hence, the Results= 25% jury marks on Fri + 25% jury marks on Sat + 50% of audience votes. The Champion with the least amount of cumulative score is then eliminated next week. This process is followed till Week 11.
Week 12: The first episode of this week, i.e. the Friday episode begins with the elimination of the Champion with the least amount of score and leaves us with the top 3 Finalists. The top 3 Champions perform and are marked by the judges. The next day, i.e. the Sat episode will see the top three finalists perform live at a ground event while the audience votes keep coming in. The cumulative score of the Jury and the audience votes finally give us the Ultimate winner- The one Champion and the Final Superstar.
So this week celebrity playback singer is Shaan and they get to sing duets with him....seems good !!!