Coming to your first query that after completion of B.Sc. IT you can appear in AIMCET to take admission in MCA.
Then after graduation you want to do either MCA or MBA.See if you are interested in your field that is in IT then it will be better go for MCA.But if you want to make your career in some other fields like management,sales or marketing then surely go for MBA.
Let me know for further assistance.
All the Best...