where I can get btech mechanical engineering previous years papers?
It would be better if you ask your seniors for the previous year question papers........
Thank you....
https://engineering.careers360.com/jee-main-college-predictor?icn=QnA&ici=qna_answer
Most of the universities in India don't release their Semester question papers pdf online. So if you don't find it on the official website of your university, you can always ask your seniors or the teachers. They will sent you and this is the case which is faced every year by most of the students.
I hope you got my point. All the very best for your future endeavors!