Ok well I'm trying to make a new game, but the thing is I'm stuck. 'Cause I don't really wanna spoil it (anyway the game is short enough), let's just say there are 2 objects.
There's object A and object B.
I want that object B to not be seen. I only want it to be revealed after the player interacts with object A. Also, the two objects are in different rooms. Plus, after using an object C on it, the object B should reveal a secret exit. The object A is NOT a container, so that's what makes it a bit difficult for me.
Also, object C must be firstly a hidden object. The object D that reveals it is not a container either. Is it the same thing as the one above, without the secret exit?
I really forgot how to do it, so please help me by telling me exactly what to do?

Thanks!

Could you give a sample transcript of how such an interaction might go (replacing the object names and any verbs with alternate names)?

Although one way would be, if you don't want object B to appear or for the player to be able to interact with it, don't put it there. Have it start in an inaccessible limbo area until the player does whatever with object A.