In this post, I will show you few ways to find out which version of SCCM 2012 is currently running in your environment, and how the cumulative update is applied. But before we start off, below I have added the list of released versions of SCCM 2012 for our easy referencing.

SCCM 2012 released versions

Below is the list of released versions of SCCM 2012 for reference:

How to find the current version of SCCM in your environment

There are several ways to find out the version of SCCM 2012 currently running in any environment, some of which are:

1. Check your devices:
   1. Open up the SCCM console, browse to Devices. (\Assets and Compliance\Overview\Devices)
   2. Depending on the size of your environment, the list of all devices should get populated
   3. Right click anywhere on the Title bar as shown below, and select Client Version 
   4. For every computer in your environment with any version of SCCM client installed, it should show you the client version, and for the most part, you should notice the same version number for all the computers if no such upgrade has ever been performed. Below is an example, illustrating one of my lab assets, showing version 5.00.7804.1000, which you can easily reference in the version table provided above to find out the version of SCCM 2012 currently installed in your environment. 
2. Check the Registry: To further confirm your findings in step 1 above, it’s always a good idea to verify version details on all of your site servers. It is important to verify all site servers if you have more than one site servers in your environment, to avoid a possibility that someone might have upgraded one of the site servers previously:
   1. Log on to the site server, launch the Registry Editor, and browse to the following location: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\SMS\Setup  Note the Full version indicates SCCM 2012 SP1 (5.00.7804.1000), while the CU version shows 0, meaning no cumulative update has been applied.

Upgrade SCCM 2012 SP1 to SCCM 2012 SP1 Cumulative Update 4

Below is the quick reference to upgrading SCCM 2012 SP1 to SCCM 2012 SP1 Cumulative Update 4, but for the most part, same process should be followed for upgrading to any other versions as well:

• Download the bits for CU 4 (https://support.microsoft.com/en-gb/kb/2922875
• Clear any pending reboots
• Install the CU4 update
• Update the boot images
• Create/Update Client Package
• Update Task Sequences

Install the CU4 Update Below are the screenshots of CU4 installation for reference:

Once the installation completes, you can go back to the registry on your site server to verify the key, which should now indicate value 4 for CULevel key, as illustrated below:

Update Client Package

Once the SCCM 2012 version has been updated, you need to upgrade the SCCM Client version on computers currently running the previous version of SCCM Client. During the CU4 installation, if the options selected, the installation automatically creates the upgrade packages for both the client and the console, as illustrated below:

All we have to do is simply distribute the content, create a device collection of target computers, and make a deployment.