Chiming in to answer as best as I can (I was part of team for this game):

- Yes, the really dense tree line forms level boundaries. Sometimes regions of trees will also separate parts of the map you can access, but the gap between them is a lot more noticeable, so there's no need to go try squeezing into the tiny spaces (unless it's to chase a bug for example)

 - When you successfully hunt a bug, you hear a slightly different sound, your hunger bar (visible on the screen at all times as several squares) goes up, and the bug disappears from the map (which may not always be clear if there are multiple bugs of the same type flying about). It's quite difficult until you get a knack for it, so it's quite likely you haven't caught a bug yet. The trick is to really SPAM  ping until you've got a kind of time lapse image of the bug's movement, and then strike to intercept (attached a screenshot showing the kind of echolocation imaging you should aim for). In the start it's a bit slow as you need to wait for swoop to come off cooldown if you miss, so you really need to pick your strikes carefully. As you fill hunger past a certain point, you unlock additional swoops. However, different bugs move differently, and some are much easier to catch than others. (For example, there's a grasshopper-like bug that moves in hops and remains completely stationary between them.)

- There is no end goal in the game other than to survive as long as possible (at least at this time)