Hello aspirant

hope you are doing great. As per your query  I would glad to tell you that mostly age of the 20-21 students get done with their 3 years bachelors . Preparation of upsc exam is something different which requires determination and dedication of next level and yes if you didnt clear upsc you will be able to persue higher studies but you will be turned into 23-24 as three years time period is minimum required for an average student to clear upsc ,so work accordingly

Hope you found this answer helpful. Good luck for your future