Dear Aspirant

hope you are doing well

Now let me go through your question

You can not cancel the registration if the modification limit is over, however, what you can try is open a new form and fill it up with another email id or if it doesn't work make some minor changes either your father's name, DOB or your name (father's name seems more safe to me) that has worked for people

But if you don't use you ssc account for a long time then it will consider as inactive user

Hope it helps

Thank you