Hello

I am extremely sorry to tell you dear but you cannot appear in UPSC examination with qualification of just to 12th

This is because,

To be eligible for UPSC examination it is mandatory to be at least a graduate in any discipline.

UPSC eligibility is provided below :-

*You must have a bachelor's degree in any discipline from a recognised university

*Minimum age limit :-  21 years

So, if you want to appear in UPSC examination then after 12th you need to pursue graduation and then only you will be eligible for UPSC

For detailed information go through

https://competition.careers360.com/articles/upsc-ias-eligibility-criteria/amp

Thank you