Most of the courses in JNU are Post graduate , M. Phil and P. hd level. If you want to study in JNU after 12th than you have very limited choice .
JNU has B.A.(Hons) program in languages like french , german , pasto, English etc.
So if you want to learn a language literature than you can apply whenever application form comes and there is entrance exam happens whom you have to qualify for admission.
Also if you qualify NDA and go training at Khadagwasala you will also get undergraduate degree from JNU.
All the best.