Hello student I'm sorry to inform you but no you can't get admission in school of open learning, University of Delhi in 3rd semester. You need to get admission in first semester and start your course right from the beginning despite of the fact that you're already in 3rd year in Agra university.

For more updates refer to the link mentioned below https://web.sol.du.ac.in/

Feel free to comment if you have any doubt

Good luck