B.Tech Scope

If you are planning to do M.Tech or Ph.D then it is advised that you go for it immediately after graduation because once you take a job, you will probably lose the motivation to go for higher studies.

M.Tech from a reputed institution is an asset in the acquisition of a job, in a reputed concern. It is not compulsory, but it is certainly an added qualification.

Being in CS, the college from which you are studying doesn't matter. You can get a job if you are well prepared. You must learn technical stuff like programming languages, databases and work on your communication skills to get through.

You should prepare for GATE and do M.Tech in a good college.

You have to qualify tests like GRE or TOEFL in order to pursue higher studies abroad. You have to apply separately for the colleges and universities. You may not get a scholarship to pursue your Master's degree abroad.

No, you don't need any work experience to pursue MBA. Candidates with work experience are preferred more as they have some first-hand knowledge of the field they want to specialise in. You should gain at least two years of work experience before pursuing MBA.

Masters in Mechatronics is the best course in mechanical engineering, mechatronics is the study of mechanical and electronics which helps to get the best job in a company.

For making a career in aviation industry after completing your B.Tech, you can go MBA in aviation management. There are many colleges that provide this specialization like:
IIM - all states : This college without a doubt is the best for MBA.
Other than this:
Andhra Pradesh Aviation academy
UPES, Dehradun
Narsee Monjee, Mumbai