Since Naruto and a lot of other people know that Minato is Naruto's father, shouldn't Naruto replace 'Uzumaki' with 'Namikaze'? After all, you usually take the last name of your father.
So yeah just like the title says: "How do you think Deidara got his extra mouths?". I personally think its some kind of Kinjutsu only he knows. If its not a personal jutsu I'm sure the amount of teen-terrorists would've considerably raisen.
The universe wouldn't be sealed seriously. That's like saying that because he stabbed a person with the Totsuka Blade the planet would also be sealed because the person is standing on it.