I recommend reading the new players guide at http://www.gamezebo.com/games/house-...es/walkthrough to get more acquainted with the mechanics of the game. If you are asking about what "referring" means, it means that if you have a patient in the ward you can pick a friend from those who joined the game when you asked and have THEM solve the case. That's a referral.
Each achievement is built into the game. I don't have a list of achievements, so the best I can tell you is to read that walkthrough for a good starting point
I did not find the right solution from the internet.