Dear student, you are not required to register again for the second round of counselling if you have already registered during the first round. It will be automatically updated in the website. You will just have to take care of the choice filling of colleges once again during the second round.

Hey, You don't need to register over and over again for counselling. once  You have registered and filled for college and branch preference then you just need to wait for counselling cutoffs to release. But if you feel so that you won't get admission in the college  in which you have applied than you can rearrange your branch and college preferences.

Hope this helps.