If it is possible but very unlikely that the condition will be fulfilled, use
if + Simple Past, Conditional (Would + Infinitive)
If I won the lottery(if + simple Past), I'd buy a big house (conditional).
You can win the lottery, it is possible, but the chance of winning the lottery is very unlikely.
If I found her address, I would send her an invitation.
I would like to send an invitation to a friend. I have looked everywhere for her address, but I cannot find it. So now I think it is rather unlikely that I will eventually find her address.
If it is impossible that the condition will be fulfilled because it refers to the past, use
if + Past Perfect, conditional (would + have + Past Participle)
If I had won the lottery (if + past perfect), I'd have bought a big house (conditional).
This means that some event/action happened in the past and, thus, you can not change it or the outcome of it. There is no chance of winning that lottery.
If I had found her address, I would have sent her an invitation.
Sometime in the past, I wanted to send an invitation to a friend. I didn't find her address, however. So in the end I didn't send her an invitation.
So, yes, you are right.
Now, coming to your second query. If you use simple present, it becomes:
If I win the lottery, I will buy a big house.
we use this conditional sentence when it is possible and also very likely that the condition will be fulfilled.
If I find her address, I’ll send her an invitation.
I want to send an invitation to a friend. I just have to find her address. I am quite sure, however, that I will find it.
More on Conditional sentences here