SharePoint: Which version or update is installed?

If you ever need a way to get the binary information of the installed SharePoint Server, you can go to the Central Administration.

Click on "Upgrade and Migration":

After that, choose "Check product and patch installation status":

On the next page you can see every binary version of the installed products on your farm or on a specific server.

PowerShell: Update a Field in SharePoint

PowerShell: Compare Dates