Army Officer

You can have any subject like Arts, Commerce, Science or engineering in your 12th class and graduation but you have to qualify the written exam and SSB for that.
To get selected as an Army Officer you must qualify one of the following exams:
After 12th - NDA followed by SSB
Or
After Graduation - CDS fol

Yes, there are many opportunities for foreign assignments and depending upon the performance armed forces officers are deputed on foreign assignments.

Army Placements are offered through selection test and interview at AIT, Pune and if you qualify the exam you can be enrolled for training in Army.

Educational requirements to take navy exams are:-
NDA : 12th
CDS : Graduation

You can have any subject like Arts, Commerce, Science or Engineering in your 12th class and graduation but you have to qualify the written exam and SSB for that.
To get selected as an Army Officer you must qualify one of the following exams:
After 12th - NDA followed by SSB
or
After Graduation - CDS fol

Approx salary of a newly commissioned army officer in the rank of Lieutenant is Rs 65,000/-.
Complete details of TES entry are as follows:-
You can apply after passing your 12th Exams. Minimum aggregate of 70% is mandatory in Physics, Chemistry and Mathematics. You will be detailed for SSB interview b

Hello Roushan,
It's nice to know that you want to join the Indian Army. Basically, you need to obtain a degree in law from a recognised university. There are too many details. For more details, visit the link mentioned below:
http://joinindianarmy.nic.in/Authentication.aspx
Best wishes.