Cn I clear BITSAT with 1 yr of preparation????

Of course you can. Infact with a solid one year preparation, you can get a very good score, if you actually study well for that one year.

BITSAT tests your speed, accuracy and clarity of concepts on a wide range of topics rather than depth of knowledge. I'm not saying it doesn't require you to have a grip on concepts, but the level of questions rarely goes beyond jee mains, or even equal to it for 70% of the questions.

So you can totally accomplish your task and get a great score if you prepare nicely.