Hello dear aspirant

Hope you’re doing well

B.A honours in any arts subject is a three year undergraduate degree course.
yes you cAn take admission in BA hons even though you studied commerce in class twelfth
if you are from commerce field in class 12th ans now want to take admission in bachelors of arts, 2.5% to 4% percentage is deducted from your best of four aggregate.

In case of university of Delhi, 2.5% is deducted.
it depends on college to college

Hope this helps

Please ask if you have any more questions

All the best for your