You can change your Minecraft client version easily through the launcher. This allows you to join servers on different versions if they support it.
- Startup your Minecraft launcher and log in using your Mojang details.
- Click on the “installations” tab at the top of the launcher and click “+ New”
- Then you can name this save, and select the version that you want to use.
- On this page, find your new installation and click the “play” button, this will select the client and start up the game.