I don't know well about "because". I think "Just because ~ year, that does not ..." is more appropriate. Is "that" skipped in the middle?

Can I use "completed" instead of "accomplished"?

Good question. "Accomplished" can be used as a synonym of "completed" and vice versa. As verbs there is however subtle nuance between them. "Accomplished" means to finish something successfully, "completed" on the other hand simply means to finish or reach the end of something. Because of this they can't always be used as synonyms of each other. In the case of this clip, "mission accomplished" means that they finished successfully. Changing it to "mission completed" means they finished the mission but doesn't necessarily mean it was successful. Ex: I completed my homework. (Finished but I don't know if it is successful until my homework is marked) Ex: I will complete my novel tomorrow. (Finish) Ex: He was very accomplished in his work. (He was successful) Ex: Did you accomplish everything you needed to? (Complete)

Which one is the most common phrase in western culture? A "Cola?" Or a "Coke?"

I'd say "Coke" is more common when referring to the brand "Coca-cola." "Cola" is just a general term for drinks like coca-cola or for that brand. So it depends on the context! Here, I'd assume they're talking about "Coca-cola" since they said "Coke." Ex: Can I get a Cola, please? Ex: I don't mind what brand of cola. Any will do.

What is "coder"?

A "coder" is someone who writes codes for computer software or programs. Ex: He graduated with a degree in computer science and became a coder.

Is there a difference between "cube" and "box?"

Yes, there is a difference! A "cube" refers to a shape with all equal sides, whereas a "box" is an object or something with a border and can be varying sizes. Ex: Write your name in the yellow box on your page. Ex: Dice are cube-shaped. Ex: Put the toys back into the box. Ex: The recipe says to cut the cheese into cubes.

How's "lawyer" different from "attorney"? I'm not sure which one to use in certain context!

Great question. "Lawyer" is a general term for a person who gives legal advice and aid. Technically, anyone who has graduated from law school can be regarded as a "lawyer". However, some "lawyers" may not practice the law in court or keep a long list of clients but they are still "lawyers". For example, after graduating from law school, a "lawyer" may become a government advisor or a company consultant. They would still be a "lawyer" even though they never go to court. The term "attorney" is actually short for attorney-at-law. It refers a member of the legal profession who represents a client in court when pleading or defending a case. A "lawyer" can be called an "attorney" if he takes on a client and then represents and acts on this person’s interest. Most legal practitioners prefer the term “attorney” since it has a more professional and dignified connotation than a “lawyer.” Ex: Every defendant deserves a good attorney. Ex: I work as a lawyer at an IT company.