I use the 4 finger up-swipe for switching apps on the ipad, not sure if that exists on the iphone. My phone is an android and I've found it consistently faster to just go home than using the damned back button.
The 4 finger gesture doesn't work, but you can double tap the home button to do the same thing (on iPad too; that's how I do it because I don't like the 4 finger gestures).
The double-tap home menu always brings up the weirdest menu. There doesn't appear to be any rhyme or reason to how the apps are arranged (or if you even get apps - sometimes you get iPod controls). One of the more irritating features of iOS.
Your device may be broken or something, because the functionality of the multi-tasking bar is pretty well defined. Double click the home button, the bar appears with a list of your most recently used apps, sorted in that order. the only way you would get ipod controls is if you swipe to the left on that bar, which reveals the media controls (works with apps besides ipod, like pandora etc).
They're arranged in order of last used; swipe left to bring up another screen's worth. Swiping right brings up music controls. It's pretty straightforward, and in my opinion incredibly useful.
How do you fit four fingers at once on a phone screen? My four fingers right next to each other are wider than my phone by a bit more than half a finger on each side.