Hi.

So when I change code inside a function, the game will continue the old function and the next call uses the new code.

What happens when I change code inside onupdate event?

onupdate;do stuffregsingleendevent

Identical to

onupdatedostuffregsingleendeventdostuff;do stuffendfunction

The same applies to events like OnUpdate. The next time OnUpdate is called, it will use the new code inside of it. The only time a function/event uses the old code is if it's in the middle of processing when the game is saved.