Hello,

In order to appear for UPSC, you need to attain 21 years age, and passed graduation in any discipline from a recognized university, there's no specific aggregate required in this case, you can appear even in the final year of graduation.

UPSC Civil Service Exam consists of three stages-

Preliminary
Mains
Interview

To give you a brief about the exam;

Preliminary consists of 200 Marks for each paper. It mainly consists of GS Paper-I consists of the following topic such as

History of India and Indian national movement, Indian and World geography, Economic and social development- sustainable development, poverty,inclusion demographics, social sector initiatives etc,Indian polity and governance-constitution,political system,Current Events nationally and Internationally, General Science,General Issues on environmental ecology,biodiversity and climate change.

In GS- I, you just need to score the required cut offs against your category.

Second paper is CSAT which is qualifying in nature (you need to score 33% which is 66 marks only) which includes topics such as basic numeracy, comprehension, logical reasoning and analytical ability, general mental ability, decision making and problem solving, interpersonal skills including communication skills.

Prelims is mcq based with each paper of 200 marks, but still it requires knowledge coupled with speed in order to ace it, it's numbers are not added in the final list,


Coming to Mains it's more of a subjective type, one needs to write answer for Four General Studies Paper such as

GS-I includes Indian Heritage and Culture,History and Geography of the World and Society,
GS-II includes Governance, Constitution, Polity, Social Justice and International Relations,
GS-III includes Technology, Economic Development, Bio-Diversity, Environment, Security and Disaster Management,
GS-IV includes Ethics, Integrity, and Aptitude
Two Optionals, One Essay, two language paper, there are total nine papers here. 250 marks for each paper, total is 1750 marks

Last stage is Personality Test of 275 marks.

You can check out the detailed information through this year official notification at https://www.upsc.gov.in/sites/default/files/Notification-CSPE_2020_N_Engl.pdf