When something is mentioned the first time, we use "this" or "that". After that, we only use "it", right?

Question

When something (a thing or an idea) is mentioned the first time, we use "this" or "that". And after that, no matter how often we refer to it, we only use "it", am I right?

For example, I made two examples:

Example 1

A: I received a scholarship for the graduate program.

B: "That" is one of the most surprising things I've heard today.

C: Congrats. I will tell "it" to our friends.

D: "It" really motivated me. B: Yeah I couldn't believe "it" at first."

Example 2

A: I received a scholarship. "That" is one of the surprising things today. I did not believe "it" when I was told about "it". However, "it" is something real.

Answer 1

The difference is more about emphasis, though it is often the case that the first occurrence receives more emphasis than subsequent ones.

In the following example, "it" is used twice for unemphatic references to the hammer, and then "that" is used to emphasise that the hammer is an unusual tool to open a window.

A: Pass me the hammer, please.
B: Here you are. What do you need it for?
A: I need it to open the window.
B: You want to open a window with that?
A: Yes, I painted the window frame yesterday, and now it's stuck closed.

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Note that a native speaker would not use "it to" in sentence C:

C: Congrats. I will tell our friends.