B.Tech

Yes, but you have to at least 70 percent to get this college.

For the branch computer science, RKGIT is a better college.

If you are scoring a rank in between 15 thousand to 20 thousand, you will be eligible.
In terms of numbers, it may be 200 to 250 marks.

You can pursue your B.Tech in civil engineering via distance education program.
https://www.shiksha.com/b-tech/colleges/distance-correspondence-b-tech-colleges-chennai

You can get admission there through JEE Mains or MHCET.
You have to score minimum 50% marks in your 12th to be eligible.
I am attaching a link which have all the information in detail.

Yes, you can change your profession to philosophy but only if you feel that it is good for you. Before going into this field, you should analyse this field and find it is compatibility with your interest.
You can find the list of best colleges in India and you can find the information regarding admission, eligibility on the same page:
https://www.shiksha.com/humanities-social-sciences/philosophy/colleges/colleges-india

Best branches by rank:
1. Computer Science & Engineering/IT
2. Mechanical Engineering
3. Electrical & Electronics Engineering
4. Electronics & Communication Engineering
5. Civil Engineering
6. Chemical Engineering
7. Architectural engineering

Best branches in terms of rank:
1. Computer Science & Engineering/IT
2. Mechanical Engineering
3. Electrical & Electronics Engineering
4. Electronics & Communication Engineering
5. Civil Engineering
6. Chemical Engineering
7. Architectural engineering