The difference is between 'hardware.screen.landscape' and 'android.hardware.screen.landscape'. When in doubt, it seems, put 'android.' at the front of anything significant that you develop for Android.
Meanwhile, I'm working on the free 'Lite' version of PCDB SuDoku Solver, and hope to have that available today as a taster app. There is a major decision to make though: should it solve games, but not let you solve them yourselves with its assistance, or the other way round. I'm leaning towards the former but am still undecided.