It is a common point of confusion because is the final supported version for several other legacy Apple devices, including the iPad (1st generation) and the iPod touch (3rd generation) . Firmware Breakdown for iPod touch 2G Final Official Version: iOS 4.2.1.
Resolved issues with HDR photo capturing and iPad network switching. Firmware Ipod 2G 5.1.1
Addressed vulnerabilities in WebKit and Safari. Modern Use for the iPod touch 2G It is a common point of confusion because
Improved AirPlay video playback and Safari Reading List syncing. Addressed vulnerabilities in WebKit and Safari
Many users mistake the 2nd generation for the 3rd generation, as they look nearly identical. However, the 3rd generation (32GB and 64GB models only) can run up to iOS 5.1.1. What iOS 5.1.1 Included (For Supported Devices)
The device is limited by its ARMv6 processor and 128MB of RAM, which are insufficient to run the features introduced in iOS 5 and later.
For devices that can run it, iOS 5.1.1 (Build 9B206) was a stability-focused update released in May 2012. Key features included: