Much like reading a chapter book, Wizard101 is sequential game play (before you move to level 2 you must complete level 1).
Even if you have purchased a Membership you must first complete all of the quests in one world to be able to move on to the next.
The same thing goes for Access to some of the streets or areas within a world. For instance, ONLY when you've successfully completed the quests for Wizard City will you be given a quest to enter into the next world, Krokotopia.
Once you have your own access there, as long as you have a Membership or have purchased the Premium area with Crowns, you will be able to enter that world freely.
Ugh i have to fight the ice boss to continue it but eh ill just get good gear and ill start crafting then ill probbly beat the whole world solo and i need to get a pet tht heals or at east have high resist