AUSTINCREATURE'S PROFILE

I just started working with RPG Maker 2003, and I'm having a lot of fun with it. I'm trying to just learn things by playing around with it, but I'm having a bit of trouble figuring out a few things.

1. How do I do a selected conversation? As in,
Person:
Hello Traveler!
Hero:
Hello!
Go away

And the player either chooses "hello" or "go away," and then the person they're talking to responds based on their choice. Say, if they choose "hello" the person will respond with, "What brings you here?" and if they choose "go away" they will respond differently?

2. How do I make objects able to be added to inventory? Like "key obtained," or "apple purchased."?

3. Once they've obtained the key, how do I make it so that a door will open only if they have the key?

4. How do I make an enemy attack the hero on sight? Like, "Stay out of its line of sight."

5. How do I make it so that a character responds based on what the hero has? Like, "I won't give you the key unless you give me something." Then when you have the something, they respond with "Thank you!" and you obtain the key?

Thank you for any help you can give!