I.

A- Yorgun görünüyorsun, yine çok geç mi yattın?- You look tired, did you go to bed too late again?

B- Evet, geç yattım.. - Yes, I did..

A -Erken yatsaydın yorgun olmazdın => you should go to bed earlier..

II.

A- Yorgun görünüyorsun, yine çok geç mi yattın?- You look tired, did you go to bed too late again?

B- Hayır, geç yatmadım.. - No, I didn´t..

A -Erken yatsaydın yorgun olmazdın => then why do you look tired? maybe you lie about the time you going to bed?  

You want to dig it deeper..

For the function you mentioned above, we use the past tense in the main clause in the present-unreal condition (when it is associated with counterfactual statements ):

Here is an example taken from one of my previous posts:

Fransızcayı iyi konuşsam Fransa´ya gezmeye giderdim.

(direct translation=> If I speak French well, I would take a trip to France )

Using the past tense in the ise clause creates the sense that an action took place.. but it may also be used for an ongoing situation and this may make the same sense as present tense does in the ise clause depending on the contex ..

Fransızcayı iyi konuşsaydım Fransa´ya giderdim. 

(direct translation=> If I spoke French well, I would take a trip to France )

I see you understand what I ment. Obviously I was trying to make a difference which doesn´t exist in language.

In English, shouldn´t it be If I spoke French well I would take a trip to France in both cases? (Henry?) This is what I ment when I said it is not only the Turkish rules but the English rules also that confuse me.

Or in English, you could also say: If I could speak French well, I would take a trip to France. But see, with even a little variation like that, can´t it change how you would say it in Turkish? If not for this example then surely many others?

And on consideration, I think they are pretty much interchangeable. And as a learner, I quite agree that its when the tense changes from "on-going" to "past", but uses the same suffix, or like how "giderdim" can denote "I would go" which is a hypothetical situation.

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Erken yola çıkarlarsa oraya zamanında varabilirler - If they leave early, they can get there on time. 

If they leave=yola çıkarlar + sa. But if its 3rd person plural, I thought this needed -seler/-salar after aorist tense? and would make çıkarsalar.  

You could say, "Fransızcayı iyi konuşabilseydim"  but it doesn´t change the meaning.. and yes, konuşsaydım and konuşabilseydim are interchangable.. at least in this sentence.. 

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I see your point..

git.se.m, git.se.n, git.se, git.se.k, git.se.niz, git.se.ler 

But when there is a tense suffix, -lar/-ler is tend to follow it:

çık.ar.lar.sa, çık.mış.lar.sa, çık.tı.lar.sa, çık.a.cak.lar.sa

Yes, ´if I spoke French well´ sounds more natural to me. It suggests that I know some French, but I am not fluent in French yet.

"If I spoke French" does not say how much French I know. It suggests I do not know much, or none.

"If I speak French well" doesn´t sound natural to me. Unfortunately I cannot explain why, using grammar rules. Something about the combination of the conditional, simple present tense and the adverb "well".

My friend speaks excellent French. If I could speak French as well as her, I would definitely travel to France. (This combination sounds fine to me.)

"If I could speak French, I would go to France" suggests that I cannot speak French, because I know no French, or not very much French. It is very similar to "If I spoke French" in my opinion.

An excellent question. My recent notes also contradict each other.

All my books and reference web-sites always use -selar/salar for 3rd person plural (they)

But recently I have noticed lerse/larsa being used by Turks. Has the language evolved?

Thanks for the clarification scalpel.

I checked some of my other notes and found Erdinc´s table of conditional suffix conjugations, where I could never see the last column. 

Below is the part I could never see 

         Gallia valisi onu durdurmaya çalıştıysa da, yenilgiye uğradı.
         Crassus köleleri kuşattıysa da, Spartaküs kuşatmayı yararak çekildi.

Another way to say ´even if´? Does it work in present tense also: aorist + -ise + de?

(Henry, I hope you don´t mind me using your thread, I hate to split things into small pieces.)

(1) 

even => de / bile

if => -se

even if => ise de / ise bile

(2) Why not?

aorist + (-se) + de / bile

gelse de, alsan da, bilsem de, etc..

Özür dilesen de affetmeyeceğim - I won´t forgive you even if you apologize

Vaktim olsa(ydı ) da (onu) yapmazdım - Even if I had time, I wouldn´t do it

Thank you, scalpel.

But there seems to be no aorist (even though I expected it). In the present tense ise attaches straight to the stem but in the past there is -di- in the middle.

         çalış|tıy|sa da

         dile|se|n de.

Just like the past condition was more real than the present. Which is true when you come to think of it.

Keep expecting.. It also could be written as this:

Gallia valisi onu durdurmaya çalışsa da başaramadı.*

*( I prefere başaramadı to yenilgiye uğradı in this sentence)