Dear Deepabhatt,

     If you are talking of AIQ by MCC then you can yes, you can as it is clearly mentioned that a candidate can register in the second round also. But, otherwise, it is not possible because if you are called for the first round and you have not registered, then your seat will be alloted to someone else and the candidate can go for an upgradation. Registration in the second round is not possible otherwise.

Wishing you all the best