Sir, which exam I have to clear for IIT entrance exam when I'm in B.SC 1st year .
What you are asking is not properly understood. Well if you want to do B.tech from IIT you need to appear JEE MAIN followed by JEE ADVANCED. After quality the latter you will be able to take admission in IIT. But if you want for M.Sc at IIT you need to qualify IIT-JAM for which the minimum qualification is graduation in the respective field. So do appear the examination for the course you want to pursue at IIT.
Hello aspirant, the criteria remains the same . You need to fill up the form as usual and just simply pay the fee and you'll be eligible to give you IIT entrance exam without any issue. If you get slected , you will require to leave your current course that's all. All the best