BBA

You question lacks clarity, there are two ways to interpret your question, either you wish to change course from your current course or your are seeking lateral entry. For the first scenario you would have to get approval from the college, but I doubt weather they will let you skip 1 st year, in the second scenario there's a 50-50 chance, but you would have to contact the college for that.

BBA stands for Bachelor in business administration
You can get jobs after completing MBA.

Look a Science student is eligible for almost all courses because he is able to do it. If you have maths background then you won't face any difficulty in pursuing BBA. BBA is a good career option.

You should start preparing for MBA. But focus mainly on BBA now because you will have to get good marks in graduation.

MMU is better because it's an A grade university.

BBA+ MBA seems a very lucrative programme. Based on my personal experience and insights from my friends who are sufferers of BBA+ MBA, I would not recommend you to go for such a programme. Below are the reasons for to validate my point:
1) A BBA (3 years ) and a MBA ( Full Time 2 years programme ) has more value in Corporate compared to the integrated ones.
2) You will have time to go for MS or MBA in other streams, which you will figure out during your BBA term.
3) MBA is more about networking. If you go for Integrated MBA, you will have a limited network. You can expand if you go for separate programs.

Hello Stuthi Without Bachelors degree you are not eligible for MBA. So, first go for BBA in mass communication. Then, go for MBA in mass communication. Thank you.