In bitsat after attempting all 150 question 12 more questions are given
Those questions are only for students who attend all the 150 quest. Its like a tie breaker only, nothing more.
YES, if you attempt all 150 questions, you get 12 extra bonus questions. But remember, once you are in the section of bonus questions, you cannot go back and review or reattempt those 150 questions.
Hope it Helps.
Thanks.