Past conditional tense usages

Dear donkadsw,
I'm happy to help.

First of all, understand that the distinction between "may" and "might" is so arcane that the GMAT will never test it. I guarantee you will not have to know that distinction on any GMAT problem. Similarly, I guarantee you will not have to know perfect forms of the conditional. It's simply not on the test. Period.

The whole topic of conditionals is somewhat rare, but it could show up on Sentence Correction in simpler tenses. At Magoosh, among our video lessons, in the Verb Form section, we have a lesson explaining all about conditionals. If you really want a thorough treatment to every grammatical structure you do have to know for GMAT SC, I would recommend checking out Magoosh.

Here, for free, is another lesson on another topic, just to give you a sense of them:
https://gmat.magoosh.com/lessons/914-the ... rb-mistake

I hope this helps,
Mike