Professional Development by joining Big 4 - please guide

My dear Friends,

I am interested in working in Mumbai Branch but would like to seek certain Clarifications regarding the same. 

I would be thankful to you if you could assist me in this exercise of mine.

Queries

1. What is the scope in working with them : in the context that whether we get exposure in various fields in relation to different types of Audit, Taxation & the like, considering that I am desperate in Practicing as a Chartered Accountant after 2 to 3 years of working with them.
2. I am currently pursuing my articleship with a small sized Chartered Accountant Firm based in Mumbai.
3. Considering the Fact that I am 21 years old also wishing of pursuing CS, LLB (taxation), CFA and specialization in IFRS do they give adequate study leave if required after qualification as a Chartered Accountant.
4. What is the usual timing of work at these firms?
5. Do the applicants have a choice of their specialization while joining them?
6. At last but not the least would you recommend me to join there, considering your experience, if any. 

Which of the big four is best fitted in the above mentioned criteria?

Hoping & waiting for your guidance for starting my professional journey

Yours truly,
Hemu Kapoor