I am trying to connect my Raspberry3 to a "Linux-Based" device. I want the RPI to get detected as a Mass Storage Device. Is this possible?
Only the Raspberry Pi Zero , Zero W , Model A and Compute Module can act as USB device. The Raspberry Pi 3 Model B can not act as USB device. This is a hardware limitation which cannot be worked around in software.
Here is a guide for the Pi Zero using ConfigFS :