All root events execute on every tick (without extra conditions), whether you specify "Every Tick" or not.
Just remember that things are executed top down in the event sheets and there shouldnt be any problems. If things dont work properly because they are spaced too far apart it just means you have events in between that affect your conditions.
I don't think this is true.
The only synchronous events are those underneath a global event. All of the global events execute asynchronously every tick, so you have no guarantee of execution order for non-conditioned global events.
EDIT: Although, I can't seem to build a basic Construct capx that shows this... so, it may be true.
They definitely execute every tick though (or as quickly as possible).