Drag and drop using combinations and multiple items?

Hello, 

I am not quite sure how to make a project work. 

I have 7 items. The items can be used to make 12 combinations. 

I've attached a visual. 

Each blue item can be dragged to the blue drop target. 

Each orange item can be dragged to the orange drop target. 

Where I am getting stuck:

1. Each item has to be able to be dragged over a total of 3 times. So if it is dragged once, it must still be available on the screen to drag over 2 more times for additional combinations. 

2. My drag-and-drop targets are invisible boxes. Depending on the combination dropped, the image (shown in yellow) needs to change states. For example, Image AD will show when A and D are dropped on the targets. 

3. Then, the image must be reset to normal for the next round (12 rounds).