Hi ! Your CGPA is very good in intermediate and also you have a decent rank in JEE mains. Well, I can say you that CSE or ECE is bit doubtful because SASTRA University is one of the best University in South. They demand bit high rank in JEE main. So hope you understand and best of luck to you.

YES, You are eligible for SASTRA university as your academic performance meets eligibility criteria of SASTRA university. They allot 30% of seats based on +2 marks, and also you have secured well, so in this category you get admission. With JEE marks, there will be little chance.

You will get ECE or CSE branch easily.