Isn't the exact same principle true of Android, with the slight distinction being that any app can multitask, not just the 5 classes of apps? Android may also kill any app whenever it wants (and prior to 2.1 or 2.2 actually did that very often, requiring always on apps to have ongoing notifications). It's just not as strict as the iOS scheduler.
Android has applications and services, services are application dedicated to running in the background. Android also provides a list of these services (Settings -> Applications -> Running Services). Normal applications, in regards to background computation, are handled in a similar way to iOS.
In principal, yes. But in my experience without any real enforcement developers do whatever they want. It drives me nuts that I have to reboot my tablet every 3-5 days. Eventually the memory is fragged to pieces and everything, especially the browser, crawls.
