DS-156 e-form mistake

I filled the ds-156 form on behalf of my parents and i made a couple of mistakes.
The form is barcoded and I have searched to no avail.
for ways to correct the mistakes.
The only information i found was;
It can be corrected by hand(but some embassies do not allow it).
The form allows you to correct questions 15 and below ONLY(which i could not do anyway)
2 days before the interview you can view your form and correct it.
Others stated that you cannot redo the process once you submit it.