Science

You may take up Physics, Chemistry, Mathematics or Physics Chemistry Biology or even Physics Chemistry Mathematics Computer Science or Physics Chemistry Mathematics Biology or Physics Chemistry Mathematics Electronics. These are all diverse combinations available in varied formats in different state

B.Sc in Chemistry would be best, if you want to go for Lectureship. You can also go for lectureship through Biochemistry, if you want. There is no foundation on restriction on the career choice after B.Sc. Both will be good for lectureship and biochemistry.

Yes, you will be able to apply after 2 years for M.Sc. You may be asked to produce an affidavit stating your reason for gap, but that can be easily managed.

Research & teaching aptitude, reasoning abilities, some basic computer concepts, English grammar & rules, are the common syllabus for any Ph.D entrance exam. Detailed bifurcation you can have from the concerned site. There are various entrance exams but this one is commonly accepted syllabus.

Post graduate Diploma in Canada will cost you between INR 15 Lacs to INR 20 Lacs. It is one year programme and in Canada, if you do this one year programme, you are allowed to stay back for one year. Only if you have done 4 year degree programme, you can do this programme. M.Sc in UK is a one year p

If you have the Pass Certificate provides by CBSE, then nothing is stopping you from pursuing Higher Education. You must have had at least 6 subjects in 12th and Math as optional. So, it could be accepted, but you won't be able to pursue any course related to Maths.

The degree is usually mailed after 4 or 5 months of publishing results. This could also be delayed by various reasons. You should better contact the university and tell them that you haven't recieved the degree yet. They will tell you all necessary information.

PDF cannot be uploaded here. But, you can easily find question paper on google now a days. If you still cannot find the practice set. You will have to visit a local book seller. They usually have Xeroxes of such papers.

No, Gujarat University doesn't have M.Sc Environmental Science as distance course. You can however pursue it regularly if you wish.
Check more about the course here.
https://www.shiksha.com/science/course/m-sc-in-environmental-sciences-gujarat-university-navrangpura-ahmedabad-270210