Q: is cydia available for the ipod 4

Wrong site for hacking advice.

We cannot discuss jailbreaking in these forums. Apple's statement on the issue can be found here:

http://support.apple.com/kb/HT3743

If you still want to proceed, you'll need to look elsewhere for advice, as well as for help should that jailbreak cause problems.

Regards.

Jailbreaking iOS voids your warranty, is not supported by Apple, and discussion of it is not allowed on these forums