Hii,
I am a senior citizen. In the old tax regime, there were special advantages in tax rates for senior citizens. Does the new tax regime allow any special exemption for interest earned by senior citizens from savings or fixed deposits? Are deductions on medical insurance premiums still available for senior citizens in the new tax regime?

As an NRI, you can not open a new PPF account. But if you had already opened your PPF account when you were an Indian resident, you can continue investing in it until its maturity. You can deposit up to ₹1.5 lakh per year, and withdrawals are allowed as per PPF rules.
And once your PPF account completes 15 years, you cannot extend it further. Extensions beyond 15 years are not allowed for NRIs.