why can not I get access to this attribute $DOPOBJECTID in group node?
(details I tried to reflect щт the picture)

for this exact functionality there is
Partition SOP, just fill the rule with
group_$DOPOBJECTID
but as I can see that you have tried it in your file and it's working, you probably want to recreate it within ForEach SOP with Group SOP for a different reason than only doing this

so you cannot access it because group name is not updated per primitive and as the dopobjectid is primitive attribute it will simply not work
you can however just get the dopobjectid of the first primitive within ForEach SOP geometry, all prims have the same value anyway so you can write this in Group Name
group_`prim(opinputpath(“.”,0),0,“dopobjectid”,0)`

or since you are using the same attribute as your ForEach Attribute you can simply use
group_`stamp(“..”, chs(“../forstamp”), 0)`

u great! all working fine!)
I wonder how long is necessary to work to know all these details?