SASTRA (Deemed to be University)

Yes, you can get admission in Sastra, but I'm not sure whether you can get your desired course.

Yes, you can apply for it. There are high chances of you getting a seat if you apply.

Hello Dhanush, approximately 9 lakh students appeared in JEE Mains exam in January. Another 1 lakh fresh candidates are likely to apply for exam in April. You have 80 percentile. Hence 20% of 10 lakh or 2 lakh students are ahead of you. Hence, you should be within mark of 224000 announced in newspapers.
Best wishes to you.

Yeah, he had chances to get seat in bioinformatics or biotech in sliding can change to mechanical or EEE.

Yes, you can expect CSE there. Till 500, there's chance to get CSE.

You can get CSE there as you are a localite.

Check here rank and college cutoff and get the opening and closing rank for the expected college and your son eligibility.
Link: https://www.shiksha.com/b-tech/resources/jee-main-rank-predictor

Yes, you can prefer mechanical engineering in this college. But you are supposed to write the entrance exam to get admission in that college. So be prepared with that and proceed.

Yes, you can. In SASTRA, 70% seats for B.Tech course are filled on the basis of JEE Main score along with prior weightage to the marks in 10+2.
30% seats in B.Tech are filled on the basis of merit drawn on the basis of marks in 10+2 followed by counselling. In the case of admission through JEE Main over 70% seats, 75% weightage will be given to JEE Main score while 25% to the marks in 10+2. In the case of admission, on the basis of 10+2 merit over 30% seats, normalized marks of each board will be considered.
Best of luck.

Yes, you can. In SASTRA, 70% seats for B.Tech course are filled on the basis of JEE Main score along with prior weightage to the marks in 10+2.
30% seats in B.Tech are filled on the basis of merit drawn on the basis of marks in 10+2 followed by counselling. In the case of admission through JEE Main over 70% seats, 75% weightage will be given to JEE Main score while 25% to the marks in 10+2. In the case of admission, on the basis of 10+2 merit over 30% seats, normalized marks of each board will be considered.
Best of luck.