Testing my Project on a phone

i found out how to setup an Android Phone for testing/debugging.
I have few more questions.
While testing on my phone, will my phone render all graphics and so on or will it run only as a Input device/Monitor and the game will be rendered by my computer?
I hear only about developing on Android, does UE4 also support iOS same as android?

The game would have to be packaged and sent to your phones memory as like a final product so i would assume that it renders all the graphics since it will be executed from your phone.