You can remove/un-install/decommission the sql install safely by following the simple steps, which are describe below.
Take the Full backup of VM
Stop the SQL services
Navigate to the Control Panel and choose Uninstall a program under the Programs section.
Find Microsoft SQL Server 20XX (64-bit)
Click Uninstall/Change, then click Remove
The SQL Server Installer will launch and list all the SQL Server Instances currently installed on the server. Choose the SQL Server instance you want to downgrade and click Next. Click Select All to remove all SQL Server components from the server for this instance and click Next. Now click Remove to begin the uninstallation operation.