Can you airplay from one iOS device to another?
Hi. Is it possible to airplay from 1 iOS device to another? Also, will audio from all apps be airplayed or only apps that support it?
no, it's not possible to airplay from one device to another. only from a computer to your speakers / airplay device, and iOS to your speakers / device. or it's possible to airplay from you iOS device to your computer, given the right software. but no, not from iOS device to device.
Answering your last question anything can be air played it does not have to have a specific app or function I have an Apple TV and a Bose airplay speaker. All of the audio from iPhone except voiceover goes to it so if I'm watching a YouTube video for example on my Bose airplay speaker the audio from that YouTube video goes that speaker. The video would stay on my phone but the audio routes to wherever you tell it.