All other operating systems I mentioned had preemptive multitasking including installable apps before iOS released. iOS limited access to background processing

All other operating systems I mentioned had preemptive multitasking including installable apps before iOS released. iOS limited access to background processing by terminating apps after 10 minutes and when resources were needed. This was a new policy not new technology. Other operating systems left background processing in users' hands deliberately. Windows Phone released 3 years after iOS. Work started earlier obviously.