greetings,

UPSC, being a graduate level exam, does not care much about your 12th percentage as long as you have passed. The eligibility criteria for UPSC is universal and lenient to ensure participation of all Indian citizens 21 years and above to contribute to the functioning of our nation. In that regard, scoring less marks in school or college is not considered a demerit.

good luck for your prep.

Yeah you can. UPSC doesn't ask any particular percentage required in your 12th for being eligible. If you have cleared your 12th and graduation with atleast 45 to 50% then you are eligible for UPSC examination. You should be atleast 21 year's for being eligible for examination. Number of attempts and relaxation will vary based on your caste.