How to use a specific version of CocoaPods
Since CocoaPods is installed through RubyGems you can use their mechanisms for doing this. As outlined here you can do this:
pod _0.34.0_ install
You can verify this is working with:
pod _0.34.0_ --version
Also I would highly advise against doing this at all. I would definitely recommend you keep CocoaPods up to date and change your Podfile as needed to adapt to new versions. At anytime your old version could stop working as expected if we bump the minimum version number.