No, it’s not necessary to take admission in college allotted by 1st round. On allotment of college in the 1st round, you’ll be given four options to select in which two options will be like

1. ACCEPT allotted seat and WANT TO PARTICIPATE in 2nd ROUND of Seat Allocation

Report to the allotted institute with necessary documents and DD & deposit either the original certificates OR Demand Draft (DD) of Rs. 1 Lakh only (Rupees One Lakh only).  

2. DECLINE/ REFUSE allotted seat and WANT TO PARTICIPATE in 2nd ROUND of Seat Allocation

This allocated seat will be vacated and the you will not be able to claim this seat. The candidate shall be eligible for 2nd Round of Counselling/Seat Allocation only after original certificates/DD with photocopies of certificates has been deposited at any AIIMS.

Note: Kindly go through the latest instruction by AIIMS 2019 before opting for any options.

Hope this helps you.