How to limit the instantiation of a prefab/object?

I will explain this in the best way I can. I want to be able to instantiate an object(or a prefab) in a certain direction until it collides with a gameobject that has the "Wall" tag. When it hits the "Wall" gameobject I would like it to resize the object so that it will never pass through the wall. Is this possible in any way? Any tips or hints would be appreciated too! Thank you, Eugen