Hello SME,

My understanding about application of past perfect tense in Cause & Effect type sentence as follows-

Since Casue happen first - Had + V3

Effect later- past tense 

But If the Effect/ Result is in - Present Perfect then Cause must be in Past tense.

Please advise if above is correct understanding and can be applied to all case.

Let’s understand a little bit of conditional tense here.

If you are talking about a universal fact or a general truth, both the causes should be in the simple present tense.

Ex- When/If water reaches 100 degrees Celcius, it boils. 

If you’re talking about a specific truth (expressing a future scenario), the if clause should be in the present tense and the effect clause will be in simple future tense (will)

If you work hard, you will succeed.

If you’re talking about a hypothetical scenario, the if clause will be in the simple past tense and the then clause will be in the past form of will- would.

If I were you, I would probably meet a doctor.

If I won the lottery, I would buy a Porsche

If you’re talking about something that has happened in the past (revisiting the past), the if clause will be in the past perfect tense (had+v3) and the effect will be in the future perfect tense (would have)

If I had prepared for the GMAT, I would have scored a 760.

If I had had money, I would have bought a car.