i have not applied under ews in jan but have so in april.what changes will occur

Hello student if you've not appeared as a ews category in Jee main and appearing with ews category in Jee April then your Jee main results will remain same as of Genral category but in Jee main April results you'll have ews ranking.

Cut offs vary every year on various factors like the level of question in the entrance examination and total number of applicants in that examination.

Feel free to comment if you have any doubt
Good luck