1.If Diablo tried to destroy the High Heavens and with it Crystal Arch which create angels (by the way if the angels are not mortal how the High Heaven never gets overpopulated,but let it) why the angels dont try to slay the Abbys where demons are born from?
I've never thought about that before, but it's a really good point. The Crystal Arch was corrupted, but assumed to be back into full swing after Diablo's death. However, this proves that it can be altered. I had always figured the Abyss to be a bit more abstract than the Crystal Arch, but that would give Hell a massive advantage over Heaven. Either this is something that I don't fully understand or there are some holes to be filled.
Why they are intrested in keeping the balance?
They aren't. Heaven wants to eradicate Hell and Hell wants to eradicate Heaven.
By the way how is that the Burning Hells never gets overpopulated?Because of the wars beetwen demonic factions?
I've thought of it a bit like a unit cap of an RTS ;)
Anyway how demonic race reproduce itself exactly?
It has been stated that some demons can mate. I'm not sure how, but it's probably the old fashioned birds and bees. Or maybe the old fashioned "carrion bats and sand wasps"
It is known that Sanctuary is different beacuse it is not created only by Heaven or by Hell?
But where are those world which are only created by ONE side?
None have been made for over 3000 years. The Worldstone has been in the hands of Sanctuary. The previously created ones have all destroyed themselves through order or chaos though.
Anyway,how is it possible to create realms without the Worldstone?
The only realms that we know of that were created without the Worldstone were the High Heavens and the Burning Hells. And I suppose possibly Pandemonium.
And if the High Heanvnes and Hells (i call H&H by now) not phisically connected what is the Source of of the Great Conflict? Different nature shouldnt cause conflict since they dont have to confront each other directly.
They fight in the realm called Pandemonium.
2.We heard a lot about different realms:relam of despair,relam of terror,relam of Sanctuary,Abbys,High Heavnes,Burning Hells (it is probably several different worlds) etc. How many are?
It's important not to confuse different types of realms. The Realm of Terror or the Plains of Despair for example are parts of The Burning Hells, but not separate realms themselves. The Burning Hells, however, as a whole is a realm. There is also The High Heavens, Sanctuary, Pandemonium, The Ether, and The Unformed Land (which may be the same as the Ether). Those are the ones that I can think of at the moment.
As we know the pristes of rathma are intrested to keep the balance between the the Heavnes and Hell,because it affect the exisctance of the whole universe. In the Diablo wiki I red that a guy from blizzard (cant find where,sorry) told that necromancers knows that if theDemons would corrupt the Sancutury that would affect several worlds,but these are not the Heavens or Hells. So what are they?
If Hell corrupted Sanctuary then the tides would be turned so vastly out of proportion that they would defeat Heaven in its entirety. Without regulation, Hell would eventually destroy all of creation from their chaos, including any pocket realms that are yet unknown to us.