greetings tanzeel:

pls refer to the following link to know the previous year cut-offs:

http://www.du.ac.in/cut-off.html

you can specialise in any one subject in the ba programme.

following is the syllabus for ba programme in economics in du:

http://www.du.ac.in/du/uploads/old-ug-courses/BA-prog/30512_Syb_BA_PROGRAMME_Economics.pdf

for history:

http://www.du.ac.in/du/uploads/old-ug-courses/BA-prog/11712_BA_Prog_History_D.pdf

for Operations research:

http://www.du.ac.in/du/uploads/Administration/AC/10072015/Annexure/10072015_Annexure-41.pdf

search for more on the official website of du i.e.:

https://www.du.ac.in/

hope this helps.

good luck