Do changes to a libraries license agreement apply to previous version?

I was just wondering, if I was to release an Arduino based library license under GNU LESSER GENERAL PUBLIC LICENSE and then further down the track update the library to 2.0 and change the license to Creative Commons (CC BY-NC-SA ) would it only apply to the version 2.0 of the library and all future updates to this library?

Or does it back date to previous releases?

Im under the impression it will only apply to the version I have released under the new license and all future releases unless I was to change the license again. Is that correct?

Is that correct?

AFIAK, the other option makes no sense as it's not possible to retroactively apply a more restrictive license.