I ran it on an iPhone 6 and it was fine. Your comment about "at least 3 apps" makes very little sense to me; iOS is notoriously aggressive with memory management, and apps must be designed to expect being killed at any time without warning, with only a few specific background tasks allowed to run (and generally for limited times with explicitly defined purposes). I'm sure my phone had upwards of a hundred apps on it, but generally speaking, only one or two were running at any given time because that's true of any iOS device.