ACR 4.3.1 is not compatible with Photoshop CS. It is only compatible with Photoshop CS3, as far as Photoshop is concerned. But, having said that, ACR 4.3.1 does have fewer options when running under compatible versions of Photoshop Elements. It is that way by design. I cannot tell you what features are missing because I have never used ACR with Photoshop Elements. If you want to take advantage of all the features ACR has to offer then you need the latest version of Photoshop.