The online docs for http://sdkdocs.roku.com/pages/viewpage.action?pageId=3114061#ifChannelStoreSincev43-GetPartialUserDa... ifChannelStore.GetPartialUserData say "Since Firmware version 5.1"

Most of the modern devices I see have a version string that looks something like this:

045.03E04016A

Which I take to mean "5.03". Questions:

1. do a I need a conditional in my code checked against the version to prevent calling a method that is not supported?
2. what am I missing on the version number extraction and/or is the documentation wrong. as it stands it doesn't look like any of the devices I see are 5.1, but that doesn't seem correct.