Will I get a 100% job after I finish my engineering from NERIST?

Since you are concerned about whether or not the institution will be able to offer you a complete 100% placement opportunity, then it is important for you to understand that an institute, regardless of its prospects, can never ensure placements. 

You definitely have a good chance of exposure in the fields of mechanical engineering, electrical engineering, and civil engineering. According to the placement highlights the highest CTC offered is 3 LPA. Most IT companies come for the placement drive. 

The institute will offer decent opportunities but you also need to put in efforts to get decent placements.