Q1: I am still confused about when I should use a for-loop and when a list comprehension.

A: First of all, it should be clear that there is nothing that a list comprehension does that a for-loop doesn't. The opposite is not true meaning in certain cases the for-loop is the only way around.

The rule of thumb is if you can do something with a list comprehension, do it as it is less code than a for-loop.