As per IRDA regulations 3.1 and 4, I understand I cant be downgraded to a policy with lower benefits and I also cant be arbitrarily downgraded.
As per policy - Source: UIIC

The entry age for this policy is between the age of 18 years and 35 years. An insured beyond 35 years shall continue to be covered under Platinum policy provided the policies are renewed with us without any break.

I wanted to understand what recourse I have. Which agencies door do I need to knock for justice and will I get justice in my favour.
In case you have a complaint or grievance, you may approach or write or e-mail to the policy issuing office, Regional Office/Head Office for redressal.

Onine: http://www.uiic.in/ugms/html/app1/uiic_grievance.jsp
Offline: https://uiic.co.in/uiiccontactus