That has nothing todo with what op is referring to. Even on iOS you have a virtual memory system, like a normal PC does. If your app runs out of ram it will page to storage and the OS handles this for you. The PS1/N64 did not have any storage beyond RAM and also no virtual memory management so you had to write all the paging from CD/Cartridge to RAM yourself. Quite a difference.

Sort of. iOS does have a virtual memory system, but it's not as forgiving as a full OS would be; applications that fail to free up memory when asked to (i.e. in a low memory situation) are killed by the OS. See also: https://developer.apple.com/library/mac/documentation/Perfor...

That should be much easier to optimize against vs having no paging at all though. Are Apps running in the background asked to free up storage or be killed before the active app needs to do the same or are they referring to the active app ?

Background apps are even worse, as by default they are suspended.

If the system requires memory the ones with higher memory footprint are the first ones to go. They aren't asked nicely, just killed.

This might have changed on newer versions though. I am typing this from memory.

Also on the Watch there are also time constraints. How quick an app is allowed to execute.

Windows Phone also has similar constraints.