You are correct on your first comment. On the other two questions, it depends. In my experience I have better luck if both parents are tetraploid. Since we don't always know the chromosome count of our lilies we just have to experiment. Keep good records of your results. I have best success with tetraploid orienpet x tetraploid trumpet. For example, I get good seed from orienpet American West x tetraploid trumpet. Orienpet lily 'Ortega' is also fertile.