differences - Different conditional clauses — "if you saw", "if you were to see", "if you had seen"

Given the following sentences, what is the difference between the conditional clauses in them?

• If you saw a lion in a thick forest, what would you do?


• If you were to see a lion in a thick forest, what would you do?

I'm asking this simple thing because it's confusing me, since there is no such thing in my native language (it's quite different from English).

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I can understand this one (it may be a different question):

If you had seen a lion in a thick forest, what would have you done?

but it's a bit confusing me. In my native language, it's always formulated as follows:

If you would have seen a lion in a thick forest, what would have you done?

Does this make any difference in English?

Answer

There is no difference in meaning between your first two examples. However, the construction with were to see is more formal and slightly antiquated.

However, there is a difference between your second two examples, namely that this one is not grammatically correct:

*If you would have seen a lion in a thick forest, what would have you done?

In English we don't use the modal verb would in the if-clause of a condition of this sort. This condition must be phrased as in your other example:

If you had seen a lion in a thick forest, what would have you done?