Forecasting GDP of India

Hello friends

I took the GDP of India from 1990 to 2019.

To forecast the GDP from 2020 to 2025, I used regression techniques in excel. Typically I used a 2nd order polynomial and got a R2 > 0.98

Now I have 3 possible results

Case 1:

GDP Data from 1990 to 2019 used. Forecasted GDP growth is 5.7% CAGR until 2030

Case 2:

GDP Data from 2000 to 2019 used. Forecasted GDP growth is 4.7% CAGR until 2030

Case 3:

GDP Data from 2015 to 2019 used. Forecasted GDP growth is 2.0%, CAGR until 2030

Now can anybody tell what is the right time frame that should have been selected to estimate the GDP growth until 2030. Is it

a) data from 1990 to 2019, forecast for 2030 CAGR = 5.7%

b) data from 2000 to 2019, forecast for 2030 CAGR = 4.7%

c) data from 2015 to 2019, forecast for 2030 CAGR = 2.0%

Assume no other data is available

Thank you