"Exactly how does that custom ROM get installed??? "
http://www.android.gs/install-...
"Does it require modification of a device? "
Absolutely!
"Hardware modifications are not stock, are they? "
I think you mean software modifications, but no they're not stock. But you can make a stock backup of the original rom.
"There has been no reported successful hack of iOS devices to install malware where the device wasn't jailbroken. "
http://www.theverge.com/2014/9...
"Now, what happens on the backend is open to interpretation and subject to debate."
No it's not, because the information is not publicly available.
"Now, what happens on the backend is open to interpretation and subject to debate."
A fanboi of what exactly? If you recall, I'm treating both Apple and Google exactly the same...Using an Android device does not always mean you're a fan of Google.
Show me an Iphone that I can install a custom rom on while avoiding all of their services and I'll buy it.
An authority is a person who can tell you more about something than you really care to know.