Spanish language Q&A Forum

Why is it "Mi abuela sabia cocinar", but "Mi abuela supo cuidarme muy bien"?  Shouldn't both sentences be in imperfect tense? My assumption is that the action is descriptive and doesn't have a definite start or end.

I have encountered real-life examples using both indicative and subjunctive with "una vez que..." and I'm just hoping to confirm or correct my understanding of how this works, please...? For examples, In an article about animals' senses of smell, in discussing the properties of volatile scent compounds I read "Una vez que se vaporiza, puede extenderse rápidamente por el aire" and in a tutorial for making tortillas mexicanas I found "Una vez que sepas cómo hacer tortillas..." I'm thinking that the first takes the indicative because its describing something factual understood to happen routinely, whereas the second takes the subjunctive because it's referring to something that from the writer's point of view hasn't happened yet or is more a hypothetical idea. Is this an accurate way to understand this or am I missing something...? If this is accurate, does it generally hold true with other, similar constructions like those discussed in this lesson? Thanks in advance, as I appreciate the help!

You wrote : "¡Cómo no, por supuesto!" but isn't it the same thing two times? What is the difference between "cómo no" and "por supuesto"?

If gustar is followed by a verb, you always use gusta, right? Example: Me gusta nadar con los delfines. VS Me gustan los delfines. 

Am I understanding that correctly? 

Why is it "El cartero pasa todos los días a las tres de la tarde" instead of ""El cartero pasa todos los días a las tres por la tarde"? I thought we learned that it should be en, a, or por to express a specific time of the day?