Yes, you can file RTI application to BBOSE.
BBOSE, is a registered Govt. Society under Societies Act. It is an Open & Distance Learning Institution, set up on the lines of National Institute of Open Schooling (NIOS), under Ministry of Human Resource Development, Govt. of India. Hence, a public authority.
You can ask for the procedure to make the corrections in your marksheet. Hence, application can be made u/s 2(f), 2(j) and 6 mentionig your personal details with the payment of requisite fees as per RTI Act, 2005.
Please visit https://onlinerti.com/how-to-file-rti-online-for-bihar