UPSC

Yes, of course. The only requirement for UPSC CSE exam is graduation. It doesn't matter what the field of graduation is.

If you want to crack UPSC CSE and you are serious for that then don't go for any other courses after graduation because it doesn't matter. You should continue preparation for the exam only.

First of all, UPSC is not an exam it is a government body which conducts various exams. If you are asking for Civil services exam under which IAS IPS and IFS falls then I suggest you to read NCERT books from class 6th to 12th of Economics, Civics, History, Geography and Science because these are the basic pillars of the examination point. After completing them you can use online contents like Mrunal Patel Sir, Study IQ and so on. But for now you must read all ncert.

Register yourself again with a new I'd and number.

I believe you meant UPSC. Yes, there are many exams conducted by UPSC for which you are eligible to apply. This include graduate level posts.

Kindly predict your college through this college predictor. The rank predicted might not be accurate, but it certainly gives an idea to the aspirant.
https://www.shiksha.com/college-predictor

The exam occurs once in a year. There are 3 levels that you need to cross. Prelims, Mains, interview. You need to give prelims which is an objective type exam after clearing it, you will be giving Mains which is a writing exam and then comes the interview. Good luck.

Hello,
I suggest you to use the Shiksha's predictor tool for more information and this will help you to predict the college according to your choice rank or percentile visit this link:-https://www.shiksha.com/college-predictor
Good Luck.