Ph.D

Phd is Not required.

Some of the best in this field are Harvard University, Swiss Federal Institute of Technology Zurich,University of Oxford,Wageningen University and Research Center,University of Queensland Australia,University of California-Berkeley,University of Montpellier and University of Cambridge among others.

Dear Pranab,
Yes, you may pursue Ph.D through distance in environmental science. For the list of the universities, you may refer the link below:
http://www.minglebox.com/science/courses/environmental-science/pg-phd-environmental-science

Hi
You may check IISC, IISER, JNU, IITs , BITS pilani and HRI Allahabad for condensed matter physics.
ICT Mumbai, NIT Calicut and Jamia Milia Islamia offer p.hd in nanotechnology. So check your suitability.

Mostly there are no colleges which offer ohd in management in chennai. You can still look for other options below.
https://engineering.shiksha.com/phd-courses-in-chennai-categorypage-2-68-1-0-0-64-123-2-0-none-1-0

Depends on your research interest. Ph.D admissions are quite different out there. You must contact the universities yourself and also see if they have the research area. NTU would be best for technology research work, also NUS is Singapore's best. Best of Luck

I think you don't have clear concept about that.
B.Sc is just Undergraduate degree where as PhD is doctors degree.
For PhD you have to first qualify different Jrf exams without which PhD is of no value . For sitting in exam of different Jrf( CSIR NET-JRF, DBT- JRF, ICMR-JRF ) of life sciences you must have post graduation degree in any subject of life science.
All the best.

Hi Pratik, you must definitely look at the reputation of a school and the research work, publications its staff has been doing and intend to do in future. How good is the school giving out financial aid, stipends, graduate research assistantship positions to international students are other criterion you must check. There are no exams as such and depends from university to university. The only exam you may have to take would be GMAT or GRE. Top business schools like Kellogg announces applications every year with requirements stated clearly on the websites, you need to keep yourself updated.