EQ that considered to be Common quarters don’t give bonus for stability as common quarter does. I have already checked it for assirian dunno and goths EQ

They only count in the sense that stuff which applies to them, also applies to the EQ. Like stuff from civics, LT and techs which gets applied to common quarters. It is like other EQ which count as farms, science, or trader quarters. They do not necessarily gain the stuff the normal quarter does. Otherwise a double counting EQ would lose -30 stability. 10 from itself, -10 from the first "count as", -10 from the second "count as".

But as I know if quarter considered to be farmer quarter, than you get all the bonuses of farmer quarter (the food for example), or you don’t?… So if it does, then common quarter should provide you bonuses of common quarter (the stability per adjacent quarter) either it is not common quarter. Maybe it is my misunderstanding, but it seems logical to me if it was working in that way

You don't get automatically all effect. But they get all effect that would normally apply to them from civics, LT, adjacency effect and infrastructures and techs. For instance the Animal Barns adds new effect to Farmer Quarters:

• +1Food on Farmers Quarters per adjacent Farmers Quarter
• +1Food on Farmers Quarter

If the EQ also counts as "Farmer Quarter" it also benefits from the Animal Barns. But they do not necessarily have the "base" production of the "base" quarter. Most of the time it is not noticeable because the EQ usually has some form of basic production from the same resource they count as.

There are a few EQ that do not have the gain from the basic FIMS quarter. The Astronomy House counts as farmer and research, does not offer the farmer workslot and has no adjacency effects itself (it only helps the base quarters to get its own adjacent effect) or the base gain from farmer. Quite a few EQ do not offer the workslot for their "count as".

Off topic, sorry for the highjack

DNLH wrote

EDIT: ninja'd by shakee, once again I wish g2g came with 'a new reply was posted in the meantime' warning when you post something.

I agree. Happened to me less than 24 hours ago, again. I did decide to create a new idea in the dedicated G2G section (not so sure it would help but... so I come by to fetch some upvote for it).

/Off topic