Do I have to choose the MBA specialization like marketing, finance, etc. in 1st year or 2nd year of MBA?

You can opt for a specific specialisation such as Marketing, Finance, HR, Operations, etc. in the second year. But try to decide the same, prior to MBA admission as it will be useful for selecting relevant profile for Summer Internship Programme.

You would have to choose your field in the second year.

You can opt for a specific specialisation such as Marketing, Finance, HR, Operations, etc. In the second year.