Under the hood on iOS is a hard place to get; especially without bricking or jailbreaking a device. There are a few tools that can provide insight into what’s on a device, and about the device, though. One is an app called SysSecInfo, available at https://www.sektioneins.de/en/blog/16-05-09-system-and-security-info.html.
Once installed, you’ll see how much CPU and memory are in use, and not in use, on your device.
Scroll down and tap on Process List to see a list of each process running on the device.
Tap Details towards the bottom of the screen to see more information about the OS build running on the device.
Overall, a handle little tool, with lots of information about devices, including how to derive whether the device has been jailbroken (although note that for each method of jailbreak detection, there’s a method for defeating detection).