Hi dear,

Hope you are doing well!

Now let's go through your question.

Yes, it is actually the last step of the counselling process in which you have to report at the designated reporting center.

You need to bring all the original documents required for the verification along with a photocopy at the reporting center.

And if you failed to attend the verification process, your admission will be cancelled. 

You are advised to attend only the reporting centre which is allotted to you.

Thank You & All the best!

JOSAA generally gives a time of about 4–5 days after the first round for reporting at RCs and 2–3 days after further rounds. Try to go on the first or second day as if your papers have any problem it can be resolved else it can become difficult on the last day.

You have to report again in case your admission system gets changed from NIT+ to IIT or vice versa.

No it is not necessary to report at the alloted institute. You can visit the nearest IIT (if you are getting admission in any IIT) or NIT (if you are getting college other than IIT).