When we talk about Unreal Past using The Third Conditional we know what really happened.

Example: "If I hadn't had a lot of money, I wouldn't have gone with her that summer and we wouldn't be together now." Here I know that I had a lot of money. I know that I went with her that summer, and I know that we are together now. "If I had had a lot of money, I would have gone with her that summer and we would be together now." Here I know that I didn't have a lot of money. I know that I didn't go with her that summer, and I know that we aren't together now.

But, what if we don't know? Example: You don't know which way was chosen by your friend, but depending on it, there could be different consequences in the past, present or future. "If she chose this way, we will meet her when we get there." (Future possible consequences) "If she didn't choose this way, we won't meet her when we get there." (Future possible consequences) "If she chose the other way, she could meet/may have met wolves." (Past possible consequences)

Another example: The speaker is someone like a police investigator and is thinking about a suspect. The speaker doesn't know for sure whether he stole the money or not, but believes that if the suspect is really guilty/really stole the money, he will leave/is going to leave the country soon. "If he stole the money, he will leave the country soon." (Future possible consequences)

Another example: You are thinking about your old friend from your childhood. You don't know what have happened to her. And you say to yourself. "If she passed her exams that day, she has a lot of money now." (Present possible consequences)

One more: I was reading Dostoyevsky’s novel and there was a sentence which I tried to translate. It is something like: “If he was with her that night we went away(the night when we went away), I will definitely kill him when I see him again.” (Future possible consequences) We want to show cause and effect connection. But we don't know whether he was with her that night or not. Sometimes we can use "Present Perfect" in 'If-clause', but sometime as in this example the time period is finished so we have to use Past Tense.

To sum up: The past cannot be changed by the present and the future. The past can only be(‘could have only been’ if you like) changed by the (earlier)past. The present cannot be changed by the future. The present can be changed by the past and the (earlier)present. The future can be changed by the past, the present and the (earlier)future. This is how our universe works. There is no other way. So:

Present → Present (Zero Conditional) (Real) If you heat ice, it melts.

Present → Future (First Conditional) (Real) If she (already)has a car, she will come to the meeting.

Future → Future (First Conditional) (Real) If it rains, we will cancel the trip.

Present → Present (Second Conditional) – We know what really happens. (Unreal) If I spoke Chinese, I would go to China every year.

Present → Future (Second Conditional) – We know what really happens. (Unreal) If I were rich, I would buy a mansion.

Future → Future (Second Conditional) – We know what is going to happen. (Unreal) If I won a lottery, I would give half the money to charity.

Past → Past (Third Conditional) – We know what really happened. (Unreal) If I hadn’t studied hard, I wouldn’t have got that job.

Past → Present (Mixed of Third and Second Conditionals) – We know what really happens. (Unreal) If I hadn’t spent all her money, she would be rich now.

Past → Future (Mixed of Third and Second Conditionals) – We know what really happens. (Unreal) If she had told me, I would arrive there earlier (I know that I’m going to be late).

Can you see what is missing?

Past → Past (??) – We DO OR do NOT know what really happened. (Real) If I came home late, she got upset. (We know) If they met each other, they probably got married. (We don’t know) (They lived 6 centuries ago so we can’t say: If they HAVE met each other, they ARE probably married.)

Past → Present (??) – We do NOT know what really happened. (Real) "If she passed her exams that day, she has a lot of money now."

Past → Future (??) – We do NOT know what really happened. (Real) “If he was with her that night we went away, I will definitely kill him when I see him again.”

Now can you spot the perfect symmetry? 6 cases which are real and 6 which are unreal to fit all the laws of the universe. These are the conditionals we have in the Russian language.

We think about a real possibility in the past (something that may or may not have happened) and its possible past OR present OR future result. You do NOT know whether it happened or not, unlike The Third Conditional(or The Second Conditional), where you DO know whether it happened or not.

The questions are:

Can we use such sentences in English?

If we can, why do some English speakers say that we can't?

Are my example sentences grammatically correct in relation to English grammar?

What do we call them (Which conditional are they)?

These questions are so common in my country because in the Russian language we use such conditionals all the time especially in literature. A lot of people ask the same questions but can't find out the answer.

Thank you thorough reader! I hope this is going to be clear for everyone.