Why comparing float values is such difficult? - unity3d

Question

I am newbie in Unity platform. I have 2D game that contains 10 boxes vertically following each other in chain. When a box goes off screen, I change its position to above of the box at the top. So the chain turns infinitely, like repeating Parallax Scrolling Background.
But I check if a box goes off screen by comparing its position with a specified float value. I am sharing my code below.
void Update () {
offSet = currentSquareLine.transform.position;
currentSquareLine.transform.position = new Vector2 (0f, -2f) + offSet;
Vector2 vectorOne = currentSquareLine.transform.position;
Vector2 vectorTwo = new Vector2 (0f, -54f);
if(vectorOne.y < vectorTwo.y) {
string name = currentSquareLine.name;
int squareLineNumber = int.Parse(name.Substring (11)) ;
if(squareLineNumber < 10) {
squareLineNumber++;
} else {
squareLineNumber = 1;
}
GameObject squareLineAbove = GameObject.Find ("Square_Line" + squareLineNumber);
offSet = (Vector2) squareLineAbove.transform.position + new Vector2(0f, 1.1f);
currentSquareLine.transform.position = offSet;
}
}
As you can see, when I compare vectorOne.y and vectorTwo.y, things get ugly. Some boxes lengthen and some boxes shorten the distance between each other even I give the exact vector values in the code above.
I've searched for a solution for a week, and tried lots of codes like Mathf.Approximate, Mathf.Round, but none of them managed to compare float values properly. If unity never compares float values in the way I expect, I think I need to change my way.
I am waiting for your godlike advices, thanks!
EDIT
Here is my screen. I have 10 box lines vertically goes downwards.
When Square_Line10 goes off screen. I update its position to above of Square_Line1, but the distance between them increases unexpectedly.

Answer 1

Okay, I found a solution that works like a charm.
I need to use an array and check them in two for loops. First one moves the boxes and second one check if a box went off screen like below
public GameObject[] box;
float boundary = -5.5f;
float boxDistance = 1.1f;
float speed = -0.1f;
// Update is called once per frame
void Update () {
for (int i = 0; i < box.Length; i++) {
box[i].transform.position = box[i].transform.position + new Vector3(0, speed, 0);
}
for (int i = 0; i < box.Length; i++)
{
if(box[i].transform.position.y < boundary)
{
int topIndex = (i+1) % box.Length;
box[i].transform.position = new Vector3(box[i].transform.position.x, box[topIndex].transform.position.y + boxDistance, box[i].transform.position.z);
break;
}
}
}
I attached it to MainCamera.

Answer 2

Try this solution:
bool IsApproximately(float a, float b, float tolerance = 0.01f) {
return Mathf.Abs(a - b) < tolerance;
}
The reason being that the tolerances in the internal compare aren't good to use. Change the tolerance value in a function call to be lower if you need more precision.