{T}: Target snow land becomes a 2/2 creature until end of turn. It's still a land.
If an affected land later loses the supertype snow, Balduvian Conjurer’s effect doesn’t end. The land will remain a creature until end of turn.
A noncreature permanent that turns into a creature can attack, and its {T} abilities can be activated, only if its controller has continuously controlled that permanent since the beginning of their most recent turn. It doesn’t matter how long the permanent has been a creature.