Dogs sleep more than us, but they wake more frequently than we do. How much and when they sleep depends on the level of activity in their environment. A dog living as a pet in the home is likely to sleep more than a dog that works for a living, like a search and rescue dog or a dog working on a farm.
In the colder winter months, some rattlesnake species enter a period of brumation, which is dormancy similar to hibernation. They often gather together for brumation in large numbers (sometimes over 1,000 snakes), huddling together inside underground rattlesnake dens or hibernacula.
Technically they do, if you consider how we seem to usually define tails, being the part of the vertebrae below where the pelvis starts. Snakes do have pelvises, albeit really modified ones, and as such they do have tails as we see them. Even humans have tails (the coccyx); it just is internal and vestigial.