Even though the phrase "couple of stories" is a plural term, is it okay to use the article "a?"

Can I call animals "who" as I refer to people?

Yes, it is okay to use "who" when referring to animals, especially in the case where you are talking directly to an animal, even though they won't be able to respond back. Since animals are living things that have their own personalities, it is fine to use the pronoun "who" when talking to them. However, it is less common to use "who" for small animals or for things that do not have human characteristics. Ex: Who are you, little kitten? Ex: Who is this dog?

What does "go out" mean here?

Here, "go out" is used to show sympathy and caring emotions to someone else. The phrase "for one's heart to go out" is commonly used in this way~ to show sympathy. Ex: Their hearts went out to the families affected by the fires. Ex: My heart goes out to you. I'm here if you need anything.

If there's a "bottom of the ninth", the opposite is "top of the ninth"?

Essentially, they're the same thing! From my understanding, the difference is which team is batting when. "Bottom of the ninth" is when the home team is batting. "Top of the ninth" is when the visiting team is batting. Ex: It's the top of the ninth, and the score is tied four to four. = It's the bottom of the ninth, and the score is tied four to four.

What does "trashing [somewhere]" mean?

To "trash a place" or "trash [somewhere]" means to deliberately, or without thinking, destroy and make a mess in the place. Ex: My house was completely trashed after the party. Ex: Try not to trash the place while I'm away.

What does "hack" and "hacker" mean?

To "[computer] hack" means to use a computer to gain unauthorized access to data in a system. Basically, it's the online version of breaking into a system. A hacker is someone who hacks, and they can be amateurs or professionals. Ex: I hacked into my school system and cancelled all the exams. Ex: Online security is important, as hackers can cause a lot of damage.