Car: '11 Impreza R Special
Join Date: 1st February 2012
Location: NSW, Australia
Thanked 962 Times in 854 Posts
You still might be able to install things, you will just need a laptop to do it.
and if the USB connect enables you to connect a PC to it.
If you can enable developer mode which is done by tapping the model info line in general>about 7 times.
Then you need to enable USB Debugging.
Once you have done that, connect the headunit to a PC.
Open a command prompt and type in adb reboot bootloader
Then it is just a matter of typing in adb install app name.apk