Für einen iPod 5G, Anfang 2014 gibt es keine neuere iOS Software als 9.3.5, dafür ist die Hardware nicht geeignet.
Diese Angabe ist keine Lüge, bis Juli 2015 wurden Geräte dieser Art gebaut. Es gibt einige Datenbanken, wo man so etwas nachlesen kann.


Quelle: MacTracker
Und bei Wikipedia kann man lesen:
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It was confirmed on June 8, 2015 at Apple's WWDC that the iPod Touch 5th generation would support iOS 9. This makes it the first and only iPod touch to support 4 major versions of iOS being iOS 6, iOS 7, iOS 8 and iOS 9. iOS 9 is said[by whom?] to feature performance improvements that may help the aging device function more smoothly. Other A5-based devices will also support iOS 9 including the iPad 2 (6 major iOS versions), the iPhone 4S (5 major iOS versions) and the iPad Mini (4 major iOS versions). iOS 9.3.5 is the last update that supports the iPod Touch 5th generation as it did not receive iOS 10 along with the iPhone 4S, iPad 2 and 3, and iPad Mini 1st generation due to hardware limitations.
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Quelle: Wikipedia, iPod Touch 5G