Install different mule runtime
There is always a need to install different mule runtime version in studio. Cloudhub provide different runtime option at the time of deployment and if any organizations is having Cloudhub environment then they might run different mule application on different mule runtime.
To install different runtime on your Anypoint Studio
Go to -> Help -> Install New Software

Select Mule Runtime for Anypoint Studio

This will show the available option as per Anypoint Studio version

Select the mule runtime version you need

Click Next

Click Finish and this will install the runtime in Anypoint Studio
To run your application on particular mule runtime then update the pom.xml app.runtime entry accordingly.

Where could I find the Mule 4 Community Edition Runtime.
https://developer.mulesoft.com/download-mule-esb-runtime/