spawn 3 object in a row at the same time ( unity )

hello everyone i am new to unity i need your help i want to create a color game that includes 2 or 3 random system . i have 3 box with different color (they are sprite ) and i want to spawn them near of each other in x axis and at the same time . then i want to change their position over time and random spawn system . and i want my player and back ground be synced to each other . for example after 10 sec i want to change the sprite of my cube from blue to green and i want the background to be changed with it.

and also i want to know how to set a system that know which box is same as the player to be triggered . thanks

( i know how to spawn obstacles but i do not know how to spawn them near of each other at the same time )

no one can help me ?