The eligibility criteria of UPSC CSE states that an aspirant of UPSC CSE examination must be of 21 years of age, on or before 1st August of the appearing year. Now as you wish to appear for the UPSC CSE, in that case you are turning 21 years old after1st August 2025, you are not eligible for the examination of UPSC CSE 2025. You have nothing to do, just prepare well and appear for the UPSC CSE 2026.

For more information regarding UPSC Prpearation tips consider the link below:

https://competition.careers360.com/articles/how-prepare-for-upsc-ias

I hope this helps. Wish you a great day!