Indian Institute of Technology, IIT Bombay

Yes you can but I don't think B Tech will be enough for that and you should also complete MS after BTech.

Yes admission in IIT is totally based on JEE advanced AIR. You must have 75% in 12th in order to give JEE advanced but admission is totally based on AIR.

Currently the topper is harsh bohra and the aggregate is 8.9.

Depends on which post u are inducted in. Normally the organisation trains you on your expertise

Yes it is there is no other way as far as I know,So the only way is by clearing JEE and then you fills choices in online couselling and Branch is alloted based on your AIR.

Teaching staff is very good as expected from such institute. A lot of research work goes on and if someone has interest there are many things going on to be a part of.

I started preparing for jee just after 10th which is according to me the best time to start. You can start from next year it will be tough you'll have to complete both year course in single year. Planning depends on your teacher the way they teaches,manage your time and give equal time to all the subjects.

The chances to get IIT Bombay seems low whereas IIT Madras is very high if you perform well in GD/PI. Last year the cut off for Bombay was 90%+ whereas for chennai was 85%+.
Also if you want,you can consider IIT Roorke and IIT kanpur. Chances seems good in these IITs also.

It depends whether the person wants to go to civil engineering field or some other fields like finance, consultancy.
Those who opt for civil highest package is around 18 lakhs.Whereas for other jobs not related to civil engineering could have a higher pay.