Ph.D

Better you contact to AISECT college for Phd in Management.

Dear anup soren. Yes it is recognized no problem. to enter into government colleges/Universities you should also clear NET-Lectureship so try for it. you are hundred percent eligible to enter into government services.

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