Below are the top coaching institutes in Delhi for GATE preparation

The gate Academy

Gate Forum

DMC Education Ltd.

Cambridge Institute Of Professional Studies

UGCNET Forum

SSC JE COACHING- LOCUS CLASSES

Nam Institute Of Professional Studies

KD Campus Pvt Ltd

Engineers Zone Education Pvt Ltd

Pathfinder Academy Pvt Ltd

All

AutoCAD is a basic software which used in every organisation government and non gorment if you are interested in CAD software then learn <a href"   https://www.tecforyou.in/2018/08/most-used-mechanical-software-in-india.html?m=1"> CATIA for 3d modelling and MATLAB for analysis<a/>

AutoCAD is the most popular software used my professionals with ME degree. If you are interested in pursuing your career as a Design Engineering, you can learn one of the design software like AutoCAD, CATIA, PTC Creo, SolidWorks, etc. In case you are interesting in analysis / simulation, you can

Yes, You can apply for Aerospace Engineering after diploma in Mechanical in Jain University. You can check the eligibility to apply with given below link.

Jain University

Mechanical engineering finds applications in every one field or the other. They are basically technology driven; hence these graduates can work in public as well as private sector companies. With the progress in the economy the scope in this field has also increased tremendously. 

There are ample opportunities for Mechanical

Overall It is a decent college. But the Placement scenario for mechanical is not very good in the college. In mechanical about 20 companies visited the campus throughout the year which recruits about 70 to 80 students. The companies visited the college are TCS, MindTree, Johnson Control, Sanmar, Costal Project

There are many specialization which you can go for as per your interest and potential -

MBA in International Business Management
MBA in Infrastructure Management
MBA in Construction Management
MBA in Banking and Finance
MBA in Insurance and Risk Management
MBA in Operational Management

Good Luck!!!