Yes, it works with Google cardboard and supports virtual reality. Also with Google cardboard version 2, its own SDK was released to the iOS developers. Also, these button collaborates with any iPhone.
Note : InstaVR supports iPhone 5 or newer, with iOS 8 or higher.

iPhone 5 or iPad Air’s head tracking might not work properly (slightly rotate automatically).
You can resolve this issue by turning “Rich Head Tracking” option off in Package > Advanced Options > Advanced Settings > Rich Head Tracking.