Want to spawn a box on other box but don't want those boxes to have same tag on each other using tag

So I have 2 bad Box and 2 Nice box [There are 2 tags assigned to each box] Box Dead1 (tag = Box1) Box Dead2 (tag = Box2) Box Nice1 (tag = Box1) Box Nice2 (tag = Box2)

I want if Box Dead 1[Red] is above then below Box Nice 2[Blue] should be there [right] but if Box Dead1[Red] is there then below Box Nice1[Yellow] should not be there [wrong]. How can I code in unity3d to get this desired output?