picture u attached is rear lower arm. Originally the skru is not there. it has been modified to make it adjustable. purpose is for camber adjustment. you do not need camber nut anymore with this double adjustable screw. with this, you can go as far as -3" camber, if you ever need it..:)
not sure how many bushes are there in whole chassis, but you do not need to purchase whole set and bring it to mechanic to install. problem will arise if you buy wrong as per our advice because this can happen. For rojak car like us, sometimes we just couldn't figure out which is from ae101 or ae92. if for me, i'll bring my car to my trusted mech, tell him to check all bushes and change whichever necessary. There is SuperPro seller in Marketplace, try search for him if you want PU bush.
AE92 & EE90 chassis is same, only major diff is a mounting point in engine bay. the rest of the diff is on cosmetic only.