I am in class 12 and I have not practice a single question from 11 and 12th chapterI have not yet started any chapter .please give me detail procedure to crack iit 2017 & cbseand I promise that I will follow it very sincerely

@ MIHIR 
if u are in this condition , then its better to focus only on 12^th as by that u can at least clear mains and also do well in cbse board exams . 
as far as board exam is concerned , then u have to only follow ncert , and some other 1-2 ref books of arihant to get 90 percent . 
and u can do that with the remaining time , do start from now onwards . 

and as far as jee is concerned , study ncert throughly frst and take out the last 37 years ques paper book of jee , that is so helpfull and do each and every ques of that alongwith exempler . 
if this much u can do then at least u can qualify in mains and also 90 percent in board if studied properly , the rest month . 
and after that from now till your 1^st preboards , u have to do do 11^th syllabus in 1 days per week , and this will include only formula recap and prev year paper practice . 
ALL THE BEST ..