To answer your first question........ you need to set it to 3d volume trigger in the trigger list. Go to "Edit" Area Triggers and select the trigger number in the list and make sure "3D Volume Trigger" is checked.
and your 2nd question: That is what Elapse is supposed to do but I just tried it on my game and it doesn't work. that's kind of odd. the only other thing I could think of is If chain..... so it looks like this.
If event(?) and never() then
if chain(20) and never() then
it would be a silly way to do it but it would work. I'm just wondering why the elapse is not working. I've used it before in DFX1 and it worked fine.
and for your last statement, I'm not exactly sure what you mean. but as for events, each event logic is not exactly tied to each other unless you set it up that way. each event has it's own trigger and it's own action.
I hope this helps you man!