Hello,
You can apply for jee advanced next year, but you will have to repeat the 1st year. You can't get admitted directly into 2nd yr. But, the schedule you are going to have is going to be very hectic. If you want to apply for jee advanced, consider taking a year off and preparing for it solely.

Hey Anish, 

Yes, you can withdraw your admission from respective B.Sc course and drop a year to prepare for IIT-JEE. And you're eligible to apply for JEE-Advanced next year! 

You can even continue B.Sc and appear the exam next year but it'll be a burden juggling between college studies and exam preparation.

Hope it helps ! Good luck buddy !