How can i put minigames Inside a 3D Third Person Game

Unity Answers is more for help on a specific question or problem you are having. For more discussion related topics, I'd suggest posting on the Unity forums at http://forum.unity3d.com/forum.php

But to give you an indication...

1. You can add a minigame as a prefab with it's own camera, then instantiate the prefab and render it on top of your 3D scene.

2. This is a very simple question and you should be at least be doing a few weeks of tutorials that will teach you this rather than asking people to show you how to do it.

3. Same answer as #2

1. You can use a UI element set to appear on a trigger. You can create an empty Game Object, give it a rigid-body that's set to trigger mode, then write a script that when the trigger is activated enables the UI element (or instantiates it if there's a lot of them.

2. You can create another trigger that when activated, loads another scene that you can specify in the code.

3. Any thing that you need to activate when the player is in a specific spot can be taken care of with a trigger.

Reference the empty game object with your trigger and check it for activation. If the trigger is activated, turn on a variable and use that variable to enable your UI element that contains your minigame or questionnaire.