hi jjustsane,

On-Demand Examination System: Secondary and Sr.Secondary Level
The change of Subject/Additional subject applied for October Public Exam will be reflected in ODES(On-Demand Examination System) after October Public Exam and simillarly applied for April Public Exam will be reflectedin ODES after April Public Exam.
There will be no On-Demand Examination during the month of April,May,October and November

For any other query best will be to contact nios directly

You can also reach to NIOS by dialing Toll free No 1800 180 9393 or by sending mail at lsc@nios.ac.in (mailto:lsc@nios.ac.in)

NIOS OFFICIAL WEBSITE LINK (https://www.nios.ac.in/)

I hope this will help!!

all the best for the future!!