Science

Yes, you can go for B.Sc. IT after your 12th with commerce as eligibility criteria for pursuing B.Sc IT in most of the top universities is pass with 50% marks in 12th class and you might have to qualify some entrance test. It will be advisable if you do your degree from a well known university and that provides prime placement opportunity, outstanding exposure and professional enhancement training. I am enlisting some of the top universities for your help:
Symbiosis University, Lovely Professional University, Institute of Law, Kurukshetra University - Kurukshetra
K. L. E. Society's Law College
LJ Institute of Law-Ahmedabad
MS Ramaiah College of Law - Bangalore
Modi Law College-Laxmangarh, Rajasthan.

Yes, maths is compulsory to pursue B.Com at UG level. Please check for the same at the eligibility criteria mentioned below:
Bachelor of Commerce (B.Com. ): Eligibility:
The basic eligibility for admission to any of the B.Com. programs is mentioned below. Candidates must pass in Higher Secondary School examination from a recognised educational board
They should have Maths and English as core subjects
Minimum 50% marks are required at 10+2 level
Although, candidates from Science and Arts stream are also eligible to apply, those with Commerce stream are preferred
There is no work experience required for the course. However, students with work experience can also apply. Regards.

I would prefer a B.Tech over a B.Sc. Owing to the following reasons:
I) B.Tech will give you a technical hand which is highly preferred by companies. A technical person is supposed to tackle problems with ease. Ii)B.Tech will give you more salary in any firm or company. B.Sc. Person will get comparatively lower salary. Iii) The syllabus of B.Sc. Is vast and it is far more then B.Tech syllabus. So if you are a decent student, you will do great in engineering. Iv) You have more career options available after B.Tech. The options after B.Sc. Are limited. V) You have an opportunity of foreign placements through B.Tech while simple B.Sc. Will not get you a foreign call.