2 devices/1 iTunes

Device 1: iPod 1st Generation, using iOS 3.1 (yeah, I know!)

Have had since new but in recent years that operating system has limited what apps could be loaded. Hence, many apps on this iPod simply have not been updated for years.

I just purchased (used)

Device 2: iPhone 4s, loaded with iOS 7.0.4

I'd love to be able to utilize the updated functions and services of the updated versions of apps I already have, but I don't want to disable those same apps currently loaded on the iPod (I plan to continue to use that device).

I suppose I could create a second Apple/iTunes account, keeping the old stuff on one, the updated apps on another, but is there another way to have different versions of the same iOS apps on iTunes; an older one that only works with iOS 3.1 and a new one that can be updated for iOS 7?

Not sure if the fact I can sync the iPhone via iCloud while the iPod needs a USB cable makes any difference but right now I'm keeping my iTunes software and Library on a MacBook Pro 4,1 and manage everything from there.

- thanks