Questions about example sentences with, and the definition and usage of "Differenciate"

A:
“What is the difference between a dissertation and a thesis?” ✅

A dissertation is a long essay on a particular subject. A thesis is the point that you are trying to prove in the dissertation.

A: must is like is something that absolutely HAS to be done.

should is like there is necessity and obligation there but it isn't as urgent at must is.

"must" ex: You must do your homework./If you want a good grade in that class you must do your homework

"should" ex: I think you should break up with him/her. (the speaker is stating so because that person isn't healthy to be with)

A: "Tell me about it." is present like if someone was talking to you right now and they were telling a story you would say: "Tell me about it." but you can also say "Tell me about that." Its the same.

Even for "I can do it." and "I can do that." its the same and you can use both of these terms and English speakers would still understand.

A: In that sentence, not really. (For example in my previous sentence, saying "In it sentence..." would be wrong.) Usually you say that when you are referring to what someone just said. You can also use it though depending on the sentence. I can't think of a case where you would say either 'it' or 'that,' and what you are asking about wasn't just mentioned. Because if it wasn't, you would say "Tell me about (insert what 'it' is). For example, "Tell me about your job."

A: The first and second one are very similar, but "tell me about it" can also be used as slang.

"Our boss is stubborn, isn't he?"
-"Tell me about it."

私達の上司は頭が固い！
-そうですね。

(Tell me about itの決まり文句はマイナスイメージの表現です)

The other two are a bit different.

"I can do it" might be used in response to somebody asking if they need help. (In my next example, one person is doing something in the present.)

"Do you need help fixing that?"
-"No, no, I can do it." (They can also say: "no, I got it.")

"I can do that" might be in response to somebody asking for help.

"Can somebody clean the bathroom?"
-"Yeah, I can do that. (The meaning is pretty much the same even if they say "I can do it.")

A: I agree. It would mean "I am not"

A: It's is pronouced "id".
I never thought about this before!