Do we have to apply separately for B.Sc (Hons) in ISI Kolkata and ISI Bengaluru?

ISI Kolkata and ISI Bengaluru do not offer BSc (Hons) program. ISI Kolkata offers B.Stat and ISI Bengaluru offers B.Math.

Also, you can only apply for one course at a time because it is seen that all the exams for admissions in the Undergraduate, Postgraduate, Diploma, and JRF courses are held on one single day. It is usually held on the second Sunday of May every year. However, the exam for the course applied jointly by ISI Kolkata, IIT Kharagpur, and IIM Kolkata is usually held in the month of February.

Other than that, for all the courses of ISI, the exam is held on that single day itself and also has the same timings. The morning objective type test is usually conducted from 10:30-12:30 pm and the afternoon session subjective type test is conducted from 2:00-4:00 pm.

So you can only opt for one single exam.