1. i don't believe you'll be at a disadvantage applying for a work permit in HK as an indian. and yes, companies are likely to help you get a work permit if they're hiring you out of an mba.
2. not really since the business language in finance will still be english most of the time. however, that being said, mandarin is always a plus.
3. speaking is more important than writing in HK since you'll only be writing english. if you're working in beijing or shanghai that might be different.
4. unlikely because Singapore deals with most of the southeastern Asian businesses, and they don't speak mandarin down there.
Oxford Round 1 - interview invite 10/30/09, admit 12/11/09, ATTENDING 2010
My Road to Oxford and INSEAD http://gmatclub.com/forum/my-road-to-oxford-sbs-and-insead-89413.html#p676253