2 You're right.  You can't understand Pika-language.  You'd better take Pikachu to someone who can understand it.  "C'mon, Pikachu," you say, "let's go.  I need to take you to someone who can help."
Pikachu shakes its head. "Pika."
You frown.  "Aww, Pikachu, why not?  I don't know what you're saying."
"Pika!  Pikachu, pika!  Chu!" Pikachu points at you.
You roll your eyes.  "Maybe it's a good thing I didn't understand that."
Then, the crowd starts noticing Pikachu.
"What's that?"
"Is that a monster?"
"Ahhh!"
Pikachu freaks.  "Pika!"  It runs toward you.  It tugs your pants (or shorts, or dress, depending on who you are).  "Pika pikachu!"
You don't need to understand Pika-language to know what he's saying this time.  You smile.
"C'mon, let's bust this joint," you say.  This time Pikachu follows you closely behind.  All right, now that Pikachu's following you, who do you go to to ask to translate?

3 Your best friend who's a little bit of a loudmouth.
4 The Pokemon expert who sits two desks away from you.