You can use the FileSystem API to access external USB storage. For more information, see Handling USB Storages and Managing File Operations.

Application data is retained when the TV is switched off or the application is updated. All application data is deleted when the application is uninstalled.

When an installed application is updated, the local Web storage on the device is unaffected. The local Web storage data is only deleted when the application is uninstalled.

No. The application cache is automatically managed by the platform.

Yes. By storing user login data in local Web storage, you can manage it in the same way as other Web storage data, including deleting it.

No. For security reasons, this behavior cannot be modified. If you want to implement additional behavior when a USB storage is connected, use the Filesystem API. For more information, see Handling USB Storages.

Make sure you have declared the "filesystem.write" privilege in your "config.xml" file. It is required for writing data to storage.