'kay, so i wasted about twelve dorfs, getting one without arms. So as long as i tested, he cannot move anything, but surprisingly, he can clean himself. Tested this twice. Got him in the messy bloody room, he was spattered alright. Then he moves to the murky pool and cleans himself.
Also he could gather crops, but couldn't move them. I guess he just bites plump helmets off the ground.
And he made rock crafts with the rock, that was left lying in the workshop.
He CAN fight by the way, by biting and kicking opponents. Not too helpful, as he cannot wear anything else, that already was on him.
He cannot pick it up-> he cannot wear it. He cannot wear armor-> he is useless in serious battle. Can bite groundhog to death though.
Tested screw pumps, he never tried to do it. No error or cancel messages. I guess you have to have arms in order to screw pump.
Next thing i try is to get a dwarf without arms, teeth, and legs. See if he can fight.
If he somehow loses all his teeth, he will bump his foes to death.
As Captain of the Guard, he will administer punishments via biting. In 40d, this resulted in armless Hammerers going about life with severed arms gripped mercilessly between their bloody teeth, but teeth have been nerfed in 31.
Also, if the dwarf is injured while fighting, if you don't dismiss him from the army, he should continue to wear the pieces of armor he still has on.
I think armless dwarves can engrave and do bookkeeping stuff...