I am very sorry. It works just fine.

Updated the code

Yes:MissingReferenceException: The object of type 'GameObject' has been destroyed but you are still trying to access it. Your script should either check if it is null or you should not destroy the object. When I click on the error it brings me to the line where I say Instantiate...terrain.transform.rotation

Still doesn't work(am getting the same first tile gets deleted but second doesn't get deleted)

Thanks fixed it but when the player is at the end of the first tile, it deletes that tile and spawns another(just like it should) but when the player is at the end of the second tile it doesn't spawn another tile and doesn't delete the second tile.

Ok but when I do this : objs.Add(terrain); then it instantly deletes terrain after launching the game. I think it's because of if (player.transform.position.z - safeZone >= (position.z - objs.Count * tileLength))

I get this error: ArgumentOutOfRangeException: Argument is out of range. Parameter name: index

There is still a gap between the tiles.

Can someone please help me

Added the position of the current tile and the correct position of the next tiles.