Well...when you play an Adventurers League game, you log your XP and treasure. There isn't an online database, so it is possible for someone to create a character that is higher level. However, there are strict requirements for character creation, so it is highly likely someone would not follow those requirements and it would be noticed. And if not noticed, the person playing the character would really just be cheating themselves, as it would limit the games they would be able to play with that character as they would quickly hit the next tier. Unfortunately, if someone really wants to cheat while playing an RPG, there is plenty of opportunity to do so. These games run on the honor system. It would be easy to not subtract hp when being injured, adding an extra plus to a die roll, or casting a spell you don't have memorized.
As for the games for 1-4 level characters, you can play a character of any level in that range if it is an Adventurers League legal character that was leveled up through play. You cannot create a character of any level but first. It is possible you will have first level characters while someone else may have a fourth level character. That is expected. The level ranges are so that you are able to play a sufficient number of games to level up your character, but it will not be seriously unbalanced by having a character of significantly higher or lower level in the group. If you have a magic user with the ability to cast Fireball, he will make short work of what should have been a challenging combat encounter designed for a lower level group.
akammer wrote:Scott is absolutely right.