Throughout the video series, Piet Van den Eynde uses the latest versions of Photoshop (CC and CC2014) available at the time of recording. If you're still running Photoshop CS6, you'll find that about 85% of the techniques and topics covered apply without any problem to your version of Photoshop as well. Generally, when a feature is exclusive to CC or CC2014, this will be mentioned in the video. As a CS6 user, this gives you the opportunity to check if these features are worth upgrading for.
Most of the actions in the EasyDodge 2.0 Panel will work as well, with the exception of the 4 Clarity (Selection) actions.'
If you're still using Photoshop CS5 or lower and you're using the Adobe Camera Raw 6 plug-in that comes with Photoshop CS5 for your raw editing, you'll find that a lot has changed with regards to the Camera Raw 8 Plug-in covered in Volume 1: there really is a big difference (and advantage in terms of workflow and image quality) to raw processing in Photoshop CS6 or CC or the equivalent Lightroom versions 4 or 5.
Of Volume 2, about 70 percent applies to Photoshop CS5.
If you're using CS5 or CS6 and want to upgrade to CC you should know that Photoshop CC is available on a subscription basis only. At launch, the price used to be $25 per month, making this prohibitively expensive for the amateur photographer. However, Adobe has considerably sweetened the deal by introducing the much cheaper Photoshop Photography Program which gives you access to the latest version of Photoshop and throws in Lightroom as well for $9.99 + tax per month (when purchased on an annual basis). More info can be found here: https://creative.adobe.com/plans/photography