I know I am not in this world yet. Soon enough I will slowly. Anyways. When you have completed the game. What happens? And another thing. I was playing the game and I was in a world where that person didn't do yet. Thing is that they are max level. How is that even possible to skip a whole world? Plus being at level 110
You can skip Wysteria. It is not preferred to skip Grizzleheim or Wintertusk, due to these worlds having progression rewards (i.e. spells, pets). There's enough experience in other worlds to make it to level 110.
After you complete the main story, you just complete it. There's nothing that holds a wizard back from taking part in other wizardly activities, like side questing, fishing, crafting, pet training, etc.
I know I am not in this world yet. Soon enough I will slowly. Anyways. When you have completed the game. What happens? And another thing. I was playing the game and I was in a world where that person didn't do yet. Thing is that they are max level. How is that even possible to skip a whole world? Plus being at level 110
The person that you talked to may have skipped Grizzlehiem, Wintertusk, Wysteria or Aquila because they're side worlds. It's impossible to skip Wizard City, Krokotopia, Marleybone, Mooshu, Dragonspyre, Celestia, Zafaria, Avalon, Azteca, Khrysalis or Polaris, so if they said they skipped one of those, they are just lying.
Angela Gem, 110
Katie GoldFountain, 110 
Nicole StarSmith, 110