So I was thinking about creating a flash light which should be really simple to create and have it but the problem I was thinking about was …
How to make it so when the light hits a floor or an object … the light coming from the flash light stops there on this floor and the object illuminates ?
hi,
you can use the platformer behavior, and when the light colides with object or floor, show it (they are supposed to be hidden) or use layers and put them in a lower layer and the flash light in upper with black background.
There is an option for sprites to not go across platforms.
I think I have give you some “light” 
hmm… I think I don’t understand what you mean very well, need more explanation.
Also what this option that make sprites not move across platforms ?
Maybe you mean separate objects option ?
take a look here
http://wiki.compilgames.net/doku.php/gdevelop5/behaviors/platformer
a sprite can’t go through a platform but can colision, when the litght collisions with platform object you can do what you want to do, for example illuminate object