Hello,

See when it comes to appearing for UPSC candidates need to pass graduation in any stream from a recognized university, even final year students are eligible to apply provisionally, there is no specific aggregate required in this case, and candidates need to attain 21 years as on 1st August of the appearing year,

now there is no such thing as if you belong to humanities stream at 10+2 or graduation level then only you qualify UPSC, why I say this? if you look at previous year toppers list they come from as diverse background as that of medical, engineering, commerce, science etc, yes humanities students have advantage of being acquainted with the syllabus in the sense they have studied the subjects already at 10+2 or graduation level, so it helps as there is considerable overlap of the syllabus of general studies and optional paper,

so you have to understand that you want to appear for UPSC with or without back-up plan, if you have interest in any professional degree courses like engineering, medical, or equivalent then you may pursue the course, there have been cases where people have worked in their relative domain prior to appearing for upsc to gain experience, you should follow this path if you're not absolutely sure for only appearing for upsc which is normal as you're still studying, in case you have interest in subjects like political science, public administration, history, geography, economics, sociology etc, then you may consider pursuing graduation in these subjects, this will help you also, but as I said it's all about  your planning, and strategy which counts for when it  comes to qualifying UPSC,