The answer is, Yes. Whoever is willing to take admission into any of the Twenty IIMs whether it's Ahemdabad campus or any other campus, a candidate must appear for CAT. CAT is a exam which is conducted by IIMs in rotation. But one has to fulfill the eligibility criterias or sectional Cutoff to get a call from IIM Ahmedabad. One have to score minimum 95 percentile and 85 percentile in all the sections like LIDR, QA, VARC.
To know more about CAT 2021 exam please go through this link
To know more about IIM Ahmedabad selection Criteria, Minimum eligibility please go through this link