A knight has to prove himself to be knighted or go through a squireship.
In some campaigns, sure. Perhaps it's hereditary? Perhaps the squireship is the early part of the Knight? It's all just labels. I mean, you could say the same about a wizard - he has to go through years of training first, so how can he be 1st level?
Someone isn't really a gladiator if he can't actually survive in the arena.
Sure he is. A crappy, inexperienced gladiator, perhaps, but a gladiator nonetheless. Every gladiator has his first fight.