The jumps can't fail. This part actually plays more like an exploration segment than a battle one: you have to enter specific doors and find and destroy parasite pods in order to unlock access to the upper half of the tree. That half will be more like a regular dungeon.
I'm afraid I can't say when I expect the next demo to be ready. So far I've been really bad at estimating how much time it'll take for the next release. It will feature a huge amount of new content so I hope it'll be worth the wait ^^