i dont believe there is any specific level you have to be to go to wintertusk, you just have to fully complete grizzleheim.
The current highest level of wizard 101 to get on a single wizard is 60 and the last world of the Spiral is Celestia.
See my answer in How do you get to other worlds in wizard 101? See my answer in How do you get to other worlds in wizard 101?
There is only one way to get the aquarium in Wizard 101. You will have to pass the level.
at level 38
You have to be level 15.
You will get a castle on Wizard 101
get membership
You must be an Ice Wizard at Level 48
48 after you get scarecrow.
You don't have to be a certain level you just have to beat wizard city
you recieve Judgement at level 28
There are no level hacks on Wizard101.