I just downloaded earlier version on my Mac 3 hours ago, Do I need re-download all of them and delete earlier version? :/
Not really. 0.9.2.1 is still the latest stable version. This is a release candidate, so is meant for testing.
I can see Gavin is not among the thanks list. Does not he contribute anymore ?
Not to this minor release, which has only a very small number of fixes. He did sign the DMG and MacOSX binaries. He certainly still contributes to the next major version (what is in git master).