When you reach $50, Google sends you the PIN in an envelope, if your address on file is correct. Indeed, if you live in the US, it will be mailed faster, but if you live outside US, it can take about 2-3 weeks. I got mine after exactly 21 days and I'm living in Europe, Romania.
Yes they will send you a PIN after you reach 50$. It can take 2-3 weeks depending on where you live and how good are postal service. If it get it lost in mail, you can request another (upto 3 times).
No you won't get your pin after 50 cents since there are possibly countless of accounts with money below $50. $50 which is probably the "signal" for Google to send you a pin.