The only actual restriction that I’m sure of is the android version which should be higher than 4.4.
If you want to use the Google Cardboard VR, your phone must have a gyroscope and the Cardboard app installed.
I’ve tested Backrooms on a Sony Xperia M2 and it worked fine. (with the “effects” option turned off)
If anyone has trouble or lag with Backrooms on their phone, they are welcome to write it here.