Q: i have an old touch can't download certain apps need ios , can ios be put on this old 8gb touch

Then you have either the original 1G or 2G iPod

To update

The Settings>General>Software Update comes with iOS 5 and later.

Connect the iPod to your computer and update via iTunes as far as your iPod model allows

iOS: How to update your iPhone, iPad, or iPod touch

A 1G iPod can go to iOS 2.2 via iTunes and iOS 3.1.3 via

Purchasing iOS 3.1 Software Update for iPod touch (1st generation)       

https://buy.itunes.apple.com/WebObjects/MZFinance.woa/wa/touchLegacyLandingPage

A 2G to 4.2.1. Requires iTunes version 10.X. If a Mac it requires OSX 10.5.8 or later. With OSX 10.4.11 you coud only go to iTunes 9.X which gets you as high as iOS 4.1

Identifying iPod models

The 1G does not volume buttons on the upper left edge

To more easily find compatible apps:

Old Apps

VintApps 3.1.3 for iPhone, iPod touch, and iPad on the iTunes App Store

apps for ios 4.2.1: Apple Support Communities

Finding iOS 4.2.1 Apps Compatible with Older Devices - Apple Club

HT4972 Touch Game 4.2.1 Apps: Apple Support Communities

apps for 4.2.1 (also works for 3.1.3)

Tip - Finding 4.2.1 apps that work on an...: Apple Support Communities

1. 4.2.1 iPod 2nd generation unable to use any...: Apple Support Communities