Hi there Mohit! Hope you're having a great day.

I would like to inform you that BIT Mesra provides lateral entry to diploma students and their is a form which needs to be filled up for the process. I am linking the form down below-:

https://bitmesra.ac.in/UploadedDocuments/adminunivpoly/files/Lateral%20Entry%20Application%20Form%2C%202019%20_Diploma%20in%20Engg_.pdf

Hope this helps. Thank you.

Hello student,

No! 
The spot round for seat allotment is the final allotment round in BIT MESRA and if few seats are left empty after spot round then they leave them empty and start with the academic session. Every year few seats(1-2) are left empty but they don't bother to fill them up.

Hope this will be helpful....