How to find which version of Magento Connect Manager to use?

The only versions of Magento which carry 2.0 are:

* Enterprise Edition 1.9-RC3 & later
* Professional Edition 1.9 & later
* Community Edition 1.4.2.0-RC1 only
* Community Edition 1.5 & later

Remains uses the connect manager version 1.0

Note: Magento 1.4.2.0-RC1 was considered a “Release Candidate” and was released in a beta state. Beta versions are not intended for production use.