Apple’s internal prototyping tools are typically utilized by quite a few internal Apple employees. For example, with the tool PurpleRestore you can restore a prototype firmware or other IPSW files to an iDevice. With PurpleSNIFF you can read hidden informations out of the iDevice.
But there are more tools… You can find images of the leaked applications on some Twitter sites.
These tools are quite hard to get and are mainly traded with money or against other internal software.
I got some different tools/apps (for macOS and iOS) and also a few firmwares with SwitchBoard Prototype OS.
Here are a some internal Applications I have: