The old woman says that Rick will become a werewolf permanently when the full moon rises that night, but the previous night's moon was a waning gibbous, which occurs just after a full moon, not before.
Rick turns into a bipedal werewolf but near the end is a four legged werewolf like the rest of the werewolves. This may be because the transformation was gradual and becoming quadrupedal was the last stage of the process.