Should have done

B doesn't read naturally to my (American) English ears. BrE may be different in the use of "Should."

C is a rephrasing of "IF" but not "EVEN IF."

Do you need to rephrase A?

Try "I don't know whether it resulted from [it] or not, but it doesn't matter."

or "Regardless of whether..."

give full context

The "have" in B and C introduces a hypothetical connotation (something which could have taken place, but it didn't, a contrary-to-fact, unreal) which isn't present in A.

Also, use
Even though

Thanks…….



I am going to rephrase the following part..



Whether the cause of the shooting was due to insufficient pre-tour cautions or poor guiding facilities, the organizers and governments from both sides should share the responsibility as well as conduct a joint investigation to clarify exactly what happened in the wee hours of Friday.

Even though the shooting could have resulted from insufficient guidance/guiding

Thanks a lot !!!

You express a possibility, thus could/may/might have, not should have, which shows an obligation.

I was thinking that in a very unprobable situation...

For example, "If he should have done that, he will be punished badly".

Here, it is very unlikely that he might have done that, so in this kind of context, sentences like that may be allowed...

This is what I have been thinking.....

This is what I have been thiking on that part of grammar.

If the possibility is very low, then for example, "If he should have done that, he will be punished badly" is correct...........

Here, it is very unlikely that he did that...

Am I thinking wrong?