So the onLoop is continuously called, i.e looping. From what you've said, you seem more or less right, although fail checks can often be implemented as their own state in the onLoop (remember, to maximise robustness, have only a single interaction per onLoop call) rather than 'sequentially'.
I'm not entirely sure what you mean by your first question regarding if and else if statements. With regards to your second question, yes - if you go down deep enough, these basic principle apply. However with more complicated scripts this detail is often abstracted away using OO concepts which is a powerful way to encode more meaning/functionality/diversity into a comparatively smaller code size.
Apa