Civil Engineering

Cannot be predicted. Depends on so many factors. But, a package of Rs.3.5 lac. Can be expected. Experience increases your pay scale.

Mechanical engineering is a major engineering and development sector, highly growing with good plateforms,
Manav Rachna University is best university in Delhi NCR with best infrastructure and faculty. The plus point of Manav Rachna University is that it offers the best placement with maximum up to 18 LPA.
http://manavrachna.edu.in/university/

You need to check the opening and closing ranks for the previous years and then, conclude whether you will get the admission or not. Check here:
http://josaa.nic.in/Result2016/result/OpeningClosingRank.aspx

As your percentage is concerned, many students have more than 80% mark in Diploma but seats in engineering colleges are limited only 10% seats.

If you have done Diploma in Construction Engineering from a recognised Polytechnic then you are eligible to seek admission in Lateral entry B.Tech degree 2nd year subject to meeting other eligibilty criteria.

There is a good chance. Coep followed by vjti is the advised sequence.

M.Tech seats are filled only through GATE exam.

Yes, I think you will definitely get the required seat. As the previous year trend shows, you can easily get the required college and the branch of your choice.