Hello Aspirant

It's a bit hard to prepare for JEE ADVANCE IN 15 DAYS .But we can hope for the best with your hardwork included.you couldn't prepare fully for it but yes you could do smart work and it would be dependent on your luck that a question came from the topic you learned. If you posses a great knowledge your fundamentals are clear you could apply those fundamental easily then you wont even need those 15 days but those kind of people are very less. so what i would like to tell you is prepare at least start preparing before 3 months to the moment  of exam.

Hope it helps

Thank you & Good Luck!!!