We have sccm 2012 R2 in single primary site with 4 test clients installed along with Endpoint protection.

We are planning to enable PXE support and test OSD.

We installed KB2905002,KB2907566, KB2907591 hotfix on SCCM server.

We see under Software Library->Packages->Configuration Manager Updates->

KB 2905002-console update,

KB2905002-server update,

KB2905002- X64 client update,

KB2905002- x86 client update,

KB 2907566-Server update, 

KB 2907591- server update.

Do we have to take any other steps in order for these updates to be successfully installed on SCCM 2012 R2 server and 4 test machines with clients.

Parvinder,

I haven't installed them personally but according to the MS KB articles:

KB 2905002:

Installation information

This update applies to Central Administration sites, primary sites, administrator consoles, and clients. Applying this update to a site server will let you create client update packages.

After the update is installed on site servers, any operating system boot images should be updated. To update boot images after the hotfix is applied, follow these steps:

1. In the Configuration Manager console, click Software Library.
2. In the Software Library workspace, expand Operating Systems, and then click Boot Images.
3. Select the boot image that you want to update.
4. Right-click and then select the Update Distribution Points action.
   
   Note This action updates all distribution points and may have an adverse effect on an environment that contains many distribution points.
5. Repeat steps 3 and 4 for all boot images that have previously been distributed.

KB2907566:

Restart information

You may have to restart the computer after you apply this update.

KB2907591 :

Restart information

You do not have to restart the computer after you apply this hotfix.

For the clients, yes, you must/should deploy the client package to them although the update addressed in 2905002 is really only an issue during OSD so its not strictly required to push out to existing systems. Same with 2 (if it even created client packages). For server packages created, those are for additional site servers if you have secondary sites or additional primary sites.