I know that for levels 1 and 2 in WaniKani, review wait times for apprentice items are halved, but I’m unsure how exactly this works. Does the shorter review time apply to all items from levels 1 and 2, or all items while you are levels 1 or 2? And if the shorter review time is able to stop applying to an item it previously applied to, what are the conditions for this occuring?
It applies to all level 1 and level 2 items. Even after you enter level 3, the level 1 and 2 items will still have the halved review times in perpetuity, even if, say, you get the items incorrect after, and they go down to apprentice again.
I think it’s just when you answer correctly during a Review, then things change to a different SRS category. They can move up or down, depending on if you answer correctly or incorrectly.
WaniKani also has (what I think is) an annoying setting that extra penalizes you and brings items way down if you make a certain number of mistakes in a review session - typos included. So, using scripts or an app like Tsurukame can improve how you interact with some of these dynamics.