1. Where exactly are private keys and other application files stored (Android 4.3)? There is no /data/data/de.schildbach.wallet/ folder on the device (looked for ../data in device storage and sd card).
2. When this app is uninstalled from a device, does it make complete cleanup, deletes all private keys, etc?
1. So far, on each device the wallet was stored at /data/data/de.schildbach.wallet/files/wallet-protobuf. The location of the app-private directory is up to your specific version of Android.
2. Yes.
If I may ask, would it be possible to modify the code to store the wallet on an USB Stick (OTG)?