You can fail out of the Academy and you can fail out two ways.
The training includes over 800 hours, including a variety of web-based courses, in four major concentrations: academics, case exercises, firearms training, and operational skills. Currently, new agent training lasts approximately 20 weeks. It's a tough regimen, but trainees don't go it alone.
Gold is the 79th element in the periodic table. it has 79 protons in its nucleus and 79 outter electrons.
He can use all five elements and yin-yang release now, due to the power of the Bijuu and The sage of the six paths, but his natural element is wind. That's also why he doesn't usually use the other elements in a fight.