How does GDevelop know which object I'm referring to?

I’m new to this program and I have a question.
I was watching this tutorial:
Now, I don’t know how does the program know that the force isn’t applied to all bullets, but only to the new one.
What if I have 2 player instances that try to stomp each other and I need to calculate who has an upper Y to stomp the other, then make one stomped and the other get points? Will the program know the difference between the player instance that is above and the player instance that is below?
I’ve had this problem with Multimedia Fusion series so I would like to know if it’s solved in this program.
Thank you.

GDevelop selects the “instances” of the object it applies the actions to according to the conditions of the event. There are also some actions that changes the list of “selected” object instances, like the “Create XX object” action that automatically select this new instance for the future actions of the event.

See “Object selection by events” section in this page : … s_concepts
There is also an example provided with GDevelop : it’s named “ObjectSelectionExplanation.gdg”.
Note : in this example, if you move the mouse on multiple tank while pressing Left mouse button, they will become green but not go back to blue, this is because there’s no event to turn back them in blue (except the first but he waits the Left mouse button to be released !).