Dear aspirant, for sastra there is no cutoff and no minimum percentile required. It is based on combined merit of 12th percentage and JEE main marks (sastra will calculate like this 12th percentage * 0.75+jee main mark * 0.25). It totally depends on the number of students applied for admission, their marks and number of seats that you will get admission to in sastra or not. If your JEE percentile was more than 90, then there were maximum chances of your admission in Sastra.

Total is 165 marks. Out of 165 marks what are your marks based on that they will give the seat. There are 351 CSE seats so you need to get rank under 351 when marks are calculated out of 165. There is no reservation on the basis of caste at SASTRA University. The only reservation you can get is through the local category. However, there is a 'Trichy quota ', a 'Thanjavur quota ', and a 'Tamil Nadu quota'.

For more information, you can check:

https://engineering.careers360.com/articles/sastra-btech-admission

Hope, it helps!