Colleges in Assam

Yes, you might have to wait around for the counselling to know that. You might get into JEC but you have more chances of getting in BVEC or JIST.

Sharing the link of the sample paper:
https://drive.google.com/file/d/0B2TUA9nKtriIU3k4dkY4ZW9WdEE/view

Yes you'll get admission in AEC. As for the branch you might get to know that in counselling.

Hi there, the dates for written exam lies between July 7 to 11 for the said course.

Economics (including Micro Economics, Macro Economics, and Problems of Indian Economy),
Accounting (including Financial Accounting, Corporate Accounting, Cost Accounting, and Management Accounting),
Business Statistics and Mathematics
Business Organization, Management, Business Law, Company Law and Income Tax Law
General Knowledge and Current Affairs

Economics (including Micro Economics, Macro Economics, and Problems of Indian Economy),
Accounting (including Financial Accounting, Corporate Accounting, Cost Accounting, and Management Accounting)
Business Statistics and Mathematics
Business Organization, Management, Business Law, Company Law and Income Tax Law
General Knowledge and Current Affairs.

As per NIT Silchar placement cell officials, the average annual package offered to students is Rs. 4 LPA and the highest annual package is Rs. 9.5 LPA during the campus placement.
Coming to teaching methodology there is a pre-decided course structure assigned to each of the departments, it depends upon the teacher who takes up that particular subject, some teachers are good at explaining the concepts while some moderate in such cases we always have video tutorials to our rescue which helps us to pass the exams.

See it is upto to you only that how you perform in your academics and in the interview. Only from that you will be able to get your package, as over here you can find packages from 7 LPA to 1.5 cr per year.

For you IIT, Guwahati ECE is the 6th best ECE in the country(my opinion after IITB, M/D, K and KGP). Placement and internship opportunities are there for students in good numbers. Most of the students get placed with good salaries in companies like Goldman, Oracle, Schlumberger, Samsung R&D, Cisco( non-core and semi-core), Qualcomm.