Engineering Entrance Exam

Yes. But, it requires four years after 10+2. So, you have to pursue your M.Sc degree.

It is nearly above 150 marks in JEE Mains and more to get admission in PDPU in petroleum engineering.

Thapar University expected cut off is obviously less than IITs and NITs but not that much less. It would safely be upto GATE score of 450 to 500 and above. There is a separate entrance exam if all seats are not filled through GATE.
You should apply for that.
Best wishes

The candidates can download DU LL.B previous year's question paper, and the answer keys online. The documents would be in easy to download format in the form of PDF files. These can be quickly found, downloaded, and are in print format in case students prefer hard copies. The screen view is clear, and no information or question would be found missing.

Yes, candidates who have completed their engineering (even in 5-years) are eligible to pursue GATE exam. Please refer to the link provided below for detailed eligibility criteria where you can check for your eligibility to appear for the GATE exams. https://www.shiksha.com/engineering/exams/gate.