MCA

Yes, you can do.
I would love to share the criteria for CEH certification.
PHP
Programming dialects
C+ or C#
Java
Linux
Database
PC Network
But make sure, do the course from the right institute. http://www.koenig-solutions.com/

You should go for Poland.

Unless you are able to clear BCA, you may not able to either MCA or MBA. You are advised to concentrate in clearing your BCA backlogs.

Yes definitely, if you want, you can pursue MCA from NIT since, you have done B.Sc in maths. But the condition is that you have to qualify NIMCET examination to pursue MCA from any of the 11 NITs providing the same. The NIMCET is a National Level Entrance Test conducted by NITs for admission to the MCA course offered by NITs. Only if you are capable of qualifying the exam with a good rank, you will be able to get an admission in the NITs.

Yes, there is no specific subject graduation is done on. You can do your graduation and get into civil services. One of the challenging task to get through civil jobs.

Everything has its own way to go. Without completing 12th if you say I want to MCA that's a joke. But your under the right path do your BCA and forward go on to do MCA. It's relevant to your option choosen and one of the best courses to.

Surely,You can get the chance but it all depends how you start your career after MCA. Getting job outside India straightforward would be difficult so you have to start from working in India and get some real time experience.
Your Chances also depends on your profile on which you are going to work and based on that what are the opportunities available outside India.
Currently, As you see one profile is Big Data/Analytics/Hadoop which is in demand whose job opportunity/requirements/demand you can find worldwide but you need to get some experience in it so which better place than India,go for it!
All the best!

Yes Why Not Global opportunities are open for the study of MCA in UK, Australia, Canada, USA and some other countries those who are offering quality education.some of the universities abroad give preference to work experience. In this case the candidates have to submit the experience certificate at the time of admission to the MCA course.
The students must possess a good score in TOFEL or IELTS.
The candidates must excel in extracurricular activities as well.