Yes you can the vampire sim can do the same as a normal sim.
Chat with our AI personalities
The same way any two sims can marry in the Sims 3
No
Firstly, The Sims 3 Supernatural is required to even get vampires and werewolves. Secondly, there is no such feature in Supernatural and thus it would be impossible to make hybrids of 2 different life forms.
Unfortunately you can not marry teens in sims 3. :(
When you begin in a Sim town (unless it is Bridgeport) there are no pre-made vampires. As the game goes on, than some pre-made Sims will become vampires. If your Sim knows a vampire, there will be a red band around the picture of that Sim.