Selecting bones(hidden too) from an armature layers?

is there a way to select all bones from a sinlge layer including those hidden but without having to touch the state of the hidden bones?

yes, it’s pretty simple. To select all the bones on the first layer (layers[0]), you iterate through all the bones and check if they are assigned to the layer

import bpy

for bone in bpy.context.object.data.bones:
    if bone.layers[0] == True:
        bone.select = True