Hello Aspirant,

See if you are seeking admission to Undergraduate courses offered in IISC then there are different channels such as KVPY, IIT-JEE (Main and Advanced) and NEET through which you can take entry into IISC and the institution has clearly mentioned that "Students desirous of applying to the Bachelor of Science (Research) Programme must take at least one of the above examinations."

So if you clear JEE-Main but unable to clear JEE-Advance then also you can apply through your JEE-Main score but note that you should qualify the certain eligibility criteria which you can check from the official website of IISC, which is given below :-

https://ug.iisc.ac.in/info_brochure.html

I hope this information helps you.

Good Luck!!