Science

You can go for B.Pharma.

First, you can do NCERT so that the concepts should be clear in mind. You can also prefer some books for practice like: RD Sharma for mathematics, DENESH or HC Verma for physics and for chemistry, NCERT is very important. You can also solve previous year question papers.

You can practice more and more question. Don't give much time on reading notes of the chapter, only read it once or twice and then do minimum 70 to 100 questions of each chapter. You can't be a master at once on any chapter, so take help from solution book at the time of doing question and practice that all 70 to 100 questions 3 times.

It doesn't happen like that. First, you have to find a company who is offering you a job there. Now it depends on the company entry requirements, whether they ask for a fresher or a person with 1, 2 or 3 years of experience.
You have to check job listing on net and apply for it. Once you get an offer from there, then you need to clear IELTS paper in GT module. Thereafter, you will get a visa.

It depends on your interest and if your score is too low, you can also apply for improvement exams in class 12th.

Both the streams are equally good, opt for the one that you love the most and are most passionate about and analyze the future work conditions, scope and growth prospects before taking admission. You can also opt for psychometric test comprising of aptitude, personality and career interest to clear confusion.
You can refer to the link mentioned below for the scope of biotechnology:
http://www.peshaa.com/Upcoming-fields/Scope-of-Biotechnology-in-India.html

Yes, you can. You should not have any backlogs.