Question regarding cat form

Will i get the chance to update the form later, since i will receive my last semester marks after my cat exam,
Secondly i have entered my total and maximum marks according to my cgpa, but the percentage is correct, will it be an issue going forward.
Lastly, does the cat grievance portal work, or in better terms is it helpful for solving application related queries or mistakes which i could have done even after paying the fees.

Also if the second one is wrong, is it serious enough for me to get disqualified from the interviews