Few questions about how we can use "it" to refer to things

Question

From my understanding of the use of "it", it has to be used after someone has used "this" or "that" to introduce the topic.

My questions:

(a) If the topic is already clear to everyone, can we use "it" directly?

(b) Are the examples I have provided below correct?

(c) Is my analysis for each example correct?

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Example (0)

A: John cheated on his girlfriend. This is a common problem among relationship.

B: Yeah, it is not something we should do.

My analysis:

The "this" and "it" here refer to the cheating action in general. And the "it" is used after the idea has been introduced with the use of "this".

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Example (1)

A: John cheated on his girlfriend.

B: That is not something we should do.

A: Yes, you're right. It is very evil.

My analysis:

The "that" and "it" here refer to the cheating action in general, and the "it" is used after the idea has been introduced with the use of "that".

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Example (2) (when the topic is clear)

(A and B witness John cheating.)

A: Hey, look. John is going out with another woman. We are not telling anyone about it.

B: Yeah, sure. And by the way, it is not something we dare to do to our girlfriends. If we did it, we would be killed by them.

My analysis: The first "it" said by A means this specific event of John's cheating

The second and third "it" both mean the action of cheating in general.

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Example (3) (when the topic is clear)

(A and B witness John cheating.)

A: Hey, look. John is going out with another woman.

B: Yes, he is. And in my case, I don't do it even though it is not illegal.

My analysis: The first and second "it" mean the action of cheating in general.

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Example (4) (when the topic is clear)

(A and B try to make a fire by rubbing sticks.)

A: Oh, God, it is so exhausting. Why is it not working?

B: It is not something we can do without training.

My analysis:

The first and second "it" both mean the ongoing action of rubbing sticks to make a fire.

The third "it" means the action of rubbing sticks to make a fire in general.

Answer 1

Q. If the topic is already clear to everyone, can we use "it" directly?

Yes. Most dictionaries define the preposition as "used to refer to that one previously mentioned", but 'previously mentioned' can include tacitly implied, or assumed to be understood. For example, "it is raining". One can say this without any prior dialogue - "it" refers to the current situation. Or, you might be sharing a view with someone and say "it's beautiful". You both know that "it" is the view, because you are both looking at 'it'.

There can sometimes be a degree of ambiguity over what "it" refers back to. For example, if you are talking about a specific person and the consequences of their actions, someone might use "it" to refer to the specific situation created by that person, or to that person's actions in general. Wider context usually helps with this.

Your examples:

Example 1 - "It" refers to "that", previously mentioned. In turn, "that" refers to the action previously mentioned (cheating). It is reasonable to assume that the person means cheating in general rather than this specific instance of cheating because they go on to say "that is not something we should do" - obviously they are not talking about cheating on someone else's girlfriend, but on their own.

Example 2 - You have two uses of "it" which are different. Firstly "it" is used by the same person who has just referred to John's specific action in going out with another woman. They aren't telling anyone about "it", meaning that specific event. The other party then goes on to refer to "it" in a similar context to example 1, to mean not repeating the action themselves, so here it is the general action, not the specific instance.

Example 3 - "It" seems to refer to the general action.

Example 4 - "It" refers to the action of trying to create fire with sticks. The narrative you provide doesn't show, but it seems safe to assume that two people both engaged in the same activity together have previously discussed what they were about to do, so for them, "it" refers back to that.