well as Magnum stated, you can join the clan if you want, he is just not accepting anyone under 18 into Easy, however once you passed BT and HJS you play with most of the other companies anyways.
No, we evaluate you in BT/HJS, but usually our faulty and/or exemplary skills point themselves out when you go through the training. The key factor is teamwork really. Without it, you really have no hope of beating the veterans unless you're a one man/woman army, but even then it would be rather tough.