Engineering

Yes, this college provides admission through JEE mains score but for you with 101491 rank you might not get CSE in this college.
You can try for other branches like IT, electronics, electrical, civil, mechanical etc.

Well GLIM takes students based on their profile. You have an average profile and also the job experience matters I.e in which domain you had an experience. And also, it takes the cream layer since it doesn't have huge strength. Only 95-99%ilers in CMAT that too with an extraordinary profile can make it to GLIM as it also takes students from other entrance exam scores.

See, change of streams is not allowed you will have to drop and reappear in the competitive exam to get desired stream.

Yes, you have a great chance for getting a good college for CSE or ECE in Andhra Pradesh on basis of your eamcet rank. You can refer the following link to predict your college on Basis of your eamcet rank. https://www.shiksha.com/b-tech/resources/ap-eamcet-college-predictor.

With this rank your chances of admission in GNIT Hyderabad are really less. You can refer to the following link to predict your chances of getting GNIT Hyderabad on basis of your eamcet rank. https://www.shiksha.com/b-tech/resources/ap-eamcet-college-predictor.

The course is called ethical hacking which is only a part of B.Tech CSE branch. Apply for that.

University ki degree ya education exam base par nai hoti, university k khud ke recognition par hoti hai. Agar pvr hai to pvt aur agar government hai to government hi rahegi.

There are 2 options complete B.Tech and give entrance exam or drop now and apply to IGNOU. Since you are from Science background the only option would be management. You can though also pursue BBA LL.B. Or BBA in which economics would be taught.

As you got a very low score at your JEE there are no chances that u would get any government colleges, I would suggest you for trying private institution for your higher education.