Wholegrain, I'll stop answering your questions, as you don't seem to know how to reply and how to thank people.

Yes, part of what is called "theatrical literature": <>Google books: <> 736 on "theatrical literature"

You should use this reference, because things like these you should have known by now, sorry ... Past Unreal Conditional http://www.englishpage.com/conditional/pastconditional.html#pastunreal

> "If he should have done that, he will be punished badly". Using should/would in the if clause is not standard English these days. It was used centuries ago, and it might still be used in here and there dialect speech, but not

>at the moment when with much curiosity, indeed, urgency, the narrator was being particularly questioned upon that point right at the time when the narrator was being questioned with much curiosity, and, IN FACT/REALLY, with urgency

By the way, I would like to extend/convey my best wishes to you and to the other members of this company. extend/convey my best wishes are more formal, high register, elegant

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

> This is the first time I am participating in such a big event. This is a bit ambiguous: - the event can be at that very time or: - the event can come in the soon-to-be future The context should clarify that. I think that in this case the

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.

Until I came here, I had given it a thought. Yes, this is all indicative mood, and I think you need past perfect here, to make clear the sequence of actions. BTW, start to distinguish your examples from your commentary, say by italicization, etc.