Maths Spl

You can take commerce, arts or humanities.

Amity Noida offers a course in M.Sc applied mathematics, however, it doesn't have a course in M.Sc maths currently. However, there may be other sister branches which offer courses in M.Sc maths. Please visit the official web site of other Amity institutes to check if they have courses in Amity maths

The entrance test consists of objective type questions and the syllabus for the same is usually from:
Real Analysis
Linear and Abstract Algebra
Calculus
Topology

You need to have maths in 12th for admission in BA economic honors.

To be eligible for BA economics (honors), it is mandatory to have mathematics as a mandatory subject.

Please refer to the link provided below for a list of careers which are available to students with a commerce background. There are a number of colleges which offer a variety of courses and I am sure you will find a viable course which he can pursue for a bright future.
Https://http://shiksha.com/ca

Yes, you can do it.

Use the link and apply different filters based on your requirements to uncover the best college for you. https://www.shiksha.com/accounting-commerce/ranking/top-commerce-colleges-in-india/97-2-0-0-0.

Yes, you can take the exam from NIOS board too.

Please refer to the link mentioned below for details regarding the NPAT exam. Details like exam dates, pattern, syllabus, application form, etc. are mentioned at the link provided below:
https://www.shiksha.com/bba/exams/npat