Hi,

For UPSC, the eligibility criteria is any graduation degree from a recognized university. So, after polytechnic diploma you cannot attend this exam. Also, Candidate should have minimum 21 years of age to attend this exam.

Here are some of the details regarding UPSC Civil Services Examination:

Civil Services examination is conducted every year by Union Public Service Commission. The exam is conducted in three phases i.e., Prelims, Mains and Interview.

1. Preliminary Phase: This is the first phases which consists of two papers and it is completely objective type exam with 200 marks each. The Paper 1 consists of General Studies and Paper 2 consists of CSAT ( Civil Services Aptitude Test ). This is just a qualifying paper for Mains phase. Marks obtained in this exam are not taken into account.
2. Mains Phase : This phase is completely subjective and a written type exam. It consists of 2 qualifying papers ( Language paper and English) and 7 papers( 1 Essay paper, 4 general studies papers, 2 Optional subject papers) which are counted for merit.
3. Interview: This is basically a personality test. For this phase the candidates are selected based on the marks obtained in Mains exam.

Depending on the Mains and Interview score the final rank will be decided. Based on your preferences the service will be allotted to you.

Click the below link to know more about this exam.

https://competition.careers360.com/articles/upsc-ias-exam-pattern

Hope it helps!