What is ‘em?

Is "thing" after "pyramid" used for emphasis?

Here, "thing" means "situation". He calls it a "pyramid thing" rather than a "pyramid situation" to show disrespect towards the situation (because he is jealous that another "villain" did the biggest crime of the century, which was stealing "the pyramids" in Egypt).

What are the synonyms of “hang on”?

"Hang on" means to hold on, wait, wait a second, just a moment. Ex: We will be there in a few minutes. Hang on, please.

Does this sentence mean "I have spent many days that I would not redo" in other words?

This sentence is very confusing. "Not a day goes by" means "every day". "I would not redo" at first appears to refer to not wanting to redo "every day", but it actually has the opposite meaning. Because he says "not a day goes by" and "not redo" (a double negative), this sentence has the meaning "I would redo every day (I've spent with you)."

What's the difference between "devil", "demon" and "satan"? Are these words are basically the same term?

Mm, this is a good question! So, "devil" and "demon" can mean the same thing. "Devil" and "satan" can mean the same thing. But, "demon" and "satan" do not always mean the same thing. Biblically, "the devil" or "satan" has followers called "demons" which are also spiritual beings. However, sometimes people refer to these "demons" or followers of "satan" as "devils"! When you say "the devil" this is in reference to "satan". "Demons" can also be a reference to trauma or issues from the past. Ex: The devil's after me, I know it. Ex: I've had demons from my past following me around for years. Ex: That creature in the movie looked like a demon! Ex: Satan won't win in my life. I won't let him.

Would it change the meaning of the sentence if I say "pass by" instead of "pass under"?

Yes, it would change the meaning! Here, the words "by" and "under" function as directional differences. When you say "pass by", it usually means to the side or next to you. However, "pass under" refers directly to underneath you or an object. If perhaps, the river was next to them and they stood on the river bank, "pass by" would be appropriate. Since they are on a bridge that is over the river, "pass under" is used. Ex: Wait for the cars to pass by before you cross the road. Ex: Charles, can you pass the ball under the bench?