I have a 4th gen Ipod and I went to download an app and it says I need ios 7. I went on google and it says a little box comes up asking if you want to download the older version of the app, but it never appears.
iPod touch (4th generation), iOS 6.1.5
Then perhaps the app you are trying to download never had a version compatible with earlier versions of iOS.
This:
'Last Compatible' Version of Apps for Users Running Legacy Versions of iOS - Mac Rumors
only works if you previously purchased the app. Otherwise there is no way to get a previous version.
How to get older versions of apps on ipod 4th gen
