In 1: Nenokkadine, there is a musical instrument shown prominently. Here is a snapshot of that instrument.
Link to that movie
This device plays some sort of piano music.
Is this a real musical instrument? If yes, then what is the name of it?
While this specific one does seem imagined, it is based on the classic Music Box mechanism, with plucked metal combs tuned to the required notes, and the addition of percussion in the form of bells.
Here is a simple example from the 1900s from Wikipedia's Music Box entry.