The question details state that you have MANY backlogs in B.Tech. and you have zero knowledge in history, economics, etc. And, you want to know if you can clear IAS exam in 8 months of preparation.
I don't think it is possible for you to do it. If you have many backlogs, it shows that you are clearly not interested in studies and you don't have the required aptitude for pursuing education. I think you should try a different profession which does not require so much study. I think you will be much happier in a profession where you like that thing rather than slogging through in something that you don't like. It will be extremely frustrating.
Studies are not for everyone. Most people don't get it. But, they easily get the example that is about to follow. Your chances of getting selected in IAS is the same as mine getting selected in the Indian cricket team with a 30+ age, 5′7″, >90kg body with no batting or bowling skills. Even if I practice for the rest of my life, I won't get selected. Is it possible? Anything is possible. Is it probable? Your guess.