You should have a new powerkey menu entry (the menu that drops down when you shortly press the powerkey) that has the CSSU logo and read CSSU features. There you can enable and disable the landscape and other features. This is at least in the CSSU-Testing based Thumb version that I have in my system.

Basically the CSSU-stable is the rock-solid and most stable version that has the features and tweaks that have been tried and tested the most and I think contains mainly fixes to the bugs that Nokia left unfixed in the last firmware. You could say it is the CSSU you should install on your mothers phone. It is in the version 6.1 as you see, and the CSSU-testing that is bit more bleeding edge is already at least in the version 8.3.

Eventually when the features and tweaks are tested enough and the devs feel that they are rock-solid stable they are introduced to the stable version.

In my own opinion the CSSU-testing is as solid as the stable and because of that I think that many everyday user use CSSU-testing on their phones. There are also many happy user using the Thumb version of the CSSU-testing like me and feel confident that the phone works as it should.

Check the changelogs for the CSSU and CSSU-stable and see the difference. It is ofcourse safer to remain on the stable, but I and many other user have installed the Testing version and continue happily using our phones.