If your mother’s surname is different in your 10th and 12th marksheets, it usually won’t lead to rejection in DU CSAS Phase 1. At most, the university might ask for clarification during document verification. You can resolve it by submitting a notarized affidavit stating both names refer to the same person. Just make sure the name in your application matches the one in your 10th marksheet.

That is normally how it is done.

No, your DU CSAS Phase 1 form won’t be rejected due to a surname difference in your mother’s name between 10th and 12th marksheets. Just use the name as per your 12th marksheet and keep both documents ready for verification if asked.