Exam

You can choose any stream of your interest because to write UPSC exams, you have to be a graduate in any course. UPSC uptakes candidates from any course. You can choose your stream according to the optional subjects also. The list of optional subjects are:
Agriculture
Animal Husbandary and Veterinary

You have very good marks and you have very fair chances of getting the colleg:
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor
You can use the above link for predicting the college. It will depend upon the college cutoff for particular branch every college has different cutoff for

Punjab University Common Entrance Test 2018 for Under Graduate programs will be held on 29 April 2018.

Hello Neha,
There are no reservations based on caste in Sastra University. You have good chances of getting a seat at Sastra. But, as the competition is too high, you may or may not get the course you wish to. Try your chances at the counselling.
All the best.

Yes, you will have to appear for GATA.

Since you are qualified but the margin from cut-off is only 1 therefore you may not get any college with this score, but there is still a chance of getting a college via counselling.
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor
Check the college by mentioning the rank.
https:/