Aditya, Maharishi Markandeshwar University is NAAC B Accredited and UGC approved university in Ambala and provides admission to several courses like B.Sc, B.Arch, MBBS, MS etc and the selections for these courses are done through different entrance examinations like JEE MAIN, NATA etc. Now, the eligibility criteria for applying to different courses and their respective entrance exams in Maharishi Markandeswar University is different for different courses and generally requires an applicant to have passed his/her 10+2 or an equivalent examination from a recognised educational board as a necessary condition in order to be eligible but since you have not elaborated about your choice of course, so I am answering your query in a generic way. Now BIHAR BOARD of OPEN SCHOOLING and EXAMINATION (BBOSE) is a recognized board from Government of India and the Ministry of Human Resource Development and the certificates from the board are valid and are applicable anywhere, so you need not worry about it and hence the passing certificate of BBOSE would be acceptable to apply for the courses at MMU,Ambala also.