Online (Firebase): Polling in groups. Offline (Nearby API): Polling or Quizzing among nearby devices.
Read the doc file. (Polling Application.pdf) https://github.com/chinmaygarg13/Polls-n-Quizes_for_Online-n-Offline/blob/master/Polling%20Application.pdf
You may also read the README file of https://github.com/chinmaygarg13/Polls_for_NearbyDevices