In many cases it's more simple and less frustrating just to write from scratch instead of figure out what the problem is.

For 7kyu you're right.

Well, ... not sure I agree. But to make everyone happy, I've done some renaming.

meh

Generally yes (if the list comp is coded properly, without anti patterns).

Regular loops have interests only when you use them while storing other specific states/variables you have to update all along the iterations. For this, a list comp would need to compute several times those data, so in this special case, they become less efficient.