1. You can change the R version by following this document we have https://docs.microsoft.com/en-us/azure/databricks/kb/r/change-r-version
2. The R version comes with each DBR (Databricks Runtime) can be find in the release note https://docs.microsoft.com/en-us/azure/databricks/release-notes/runtime/releases

Note that, the SparkR may not work if the upgrade to a different R version. But your use case should work fine.