is there a modifier for walls?
if not,i would certainly put my batt on defensive mode to gain more def against range attack.

Didn't understand that one, can you rephrase it?

Battering Rams 24-36 damage with 8 atk and 20 def

okie let say i have 50 pop(stack 1) of it
i`ll attack this wall with 100%bp

another stack also with 50 pop(stack 2) too attacks this wall with 100%bp but is on defensive mode

so ....will there be less damage done by the second stack?
that came to this question that is there a modifier for walls(or buildings)-the def

because if there is certain def point for the walls,the second stack will certainly do less damage because of its less attack point

if no matter what the atk point for batt will do the same damage....wouldnt it be better for me to put it on def mode to resists more range attack from the enemy?...

Quite possibly, but it assumes you will not have to move the ram, and you can afford to use half a turn's BP on shielding yourself. I argued with Req for ranged shielding for a reason

If you only need one hole to invade through, that's ok - but in most games, let alone most WOL battles, a single point to invade through is not enough. You need multiple holes to stretch the defenders and force weak points.

But it depends a lot on your situation

i have 2 stack of batts and 2 stack of cats

but the war is over already
i penetrated into the castle anyway