I am trying to explain conditional3(or past conditional). Does the following explanation make sense?
You cannot change the past. That is, no matter what you imagine, the chance of you changing the things that happend in the past is zero percent. You can express this using the following structure. If ... past...... would have past participle.
Oh. Well, I see no point in the 2nd sentence; it is does not explain the first at all; it just confuses the reader.
You cannot change the past. What's done is done. You can express this using the following structure: "If + past perfect verb form, ... would have + past participle."