B.Tech

Yes, you can take entrance exams for B.Tech and since you have already done Diploma in metallurgy engineering, so you can directly take admission in the B.Tech 2nd year through lateral entry.

If you gets placed through open camps/on-campus placement, then working for 1/2 year before option for MBA is a good option. Although your academic profile is good, you can attempt CAT this year and try to score 95 percentile. Pursuing MBA from any of top 15 B-Schools is worth. So you if you have op

Core subjects in Mechanical are-
Drawing (Graphics, Machine Drawing, Production Drawing) - language of Mechanical Engineers, Mechanics of Materials (Strength of Materials), Material Science
Theory of Machines (Kinematic and Dynamic), Fluid Dynamics (Fluid Mechanics)
Thermodynamics, Machine Design, Heat

Below are some known colleges for Engineering in and around Delhi/NCR-
Indian Institute of Technology, Delhi (IITD)
Delhi Technological University (DTU)
Netaji Subhas Institute of Technology (NSIT)
Jaypee Institute of Information Technology.
Maharaja Agrasen Institute of Technology (MAIT)
Galgotias Educat

You have good chances to convert but your graduation percentage is on the lower side. Still if you perform well in GD/PI, then you have good chances to convert. As B-Schools give weightage to GD/PI-WAT/PI rounds.

There arr minor variations in syllabus of B.Tech CSE in different universities. Please find syllabus of GGSIPU for B.Tech CSE: http://ipu.ac.in/syllabus/affiliated/sybtechcse.htm. You may study syllabus to have an idea on subjects thought during B.Tech CSE.

Hello,
Yes, it is possible to pursue CCNA along with B.Tech. Many students opt for part time courses during B.Tech. I understand that it does increase the work load, but it is not too tough. All it requires is efficient time management, sincerity and determination to pursue any course you want.

Eligibility criteria for software engineering degree is PCM subjects in 10+2. If you do not have physics and chemistry as subjects, you will not able to seek admission in B.Tech CSE/ IT, but you are eligible to seek admission in BCA-MCA to pursue a career in software engineering.