Why does Tails have two tails, are SEGA trying to create a mutant?

no theye had to find away of making him fast unuf to keep up with sonic without being able to go faster they thought of this and thene put ways in the first sonic and tails of how tails could help sonic (:

Tails is that yellow, twin-tailed fox, right?

I don't know, I never really looked into it.

... And, who is this "SEGA"..?

Yes.