You can change the Ruby on Rails version in your Plesk control panel:
- Login to your UWS control panel.
- On the top menu go to Services > My Services.
- On the right side of your hosting product, click the magnifying glass to manage product.
- On this Product Details page, under the Hosting Information tab, click on the button "Login to Plesk Control Panel"
- Click on the website you would like to access Ruby for to expand it, if not already expanded.
- Under Dev Tools, click on Ruby
- Click on the current Ruby version to select a version to change to.