Not sure what you mean.. All actions inside the loop are finished for each instance, before processing the next instance. Instances are processed one by one, not all at once. But the whole loop happens in one tick.
If you need to add a delay between each loop iteration, you can do this:
For each Sprite
Wait loopindex*0.5
Sprite set visible
Your sprites will become visible one by one with 0.5 delay.