Ph.D

There are some universities such as IGNOU offer Ph.D in nursing.
The eligibility criteria for Ph.D Nursing is as follows:
1. Nursing professionals, who have completed their M.Phil degree with 55% marks from a recognized university are eligible for Ph.D.
2. Nursing, with 55% marks and five years of teaching, industry, administration, professional and clinical experience are eligible for Ph.D.
3. Nursing personnel, who have completed their M.Sc nursing with 55% marks (50% marks for SC and ST candidates).

For Ph.D in chemistry, you should have completed M.Sc chemistry with at least 55% and you have to clear Ph.D entrance exam conducted by the universities. If you have cleared NET in chemical sciences, you are exempted from giving entrance, but you have to appear for interview as required by the universities.

You can do PhD while doing a teaching job.

No, you get it once you complete MSc. During M.Phil period, you get the grant which continues till the PhD.

If your PhD degree is awarded by a UGC recognised university then it is admissible for jobs in both government and private sector.

R&D and teaching are two best options after Ph.D in life sciences.

You can check the below mentioned link:
https://www.shiksha.com/engineering/colleges/ph-d-colleges-india?sp[]=108