Develop Reference

How to prevent character from going through walls. Unity

I'm new to unity here and I have a capsule for a player and a moving wall. When ever the player touches the wall, it can just go through and walk out the other side, and I kind of don't want that. The screenshot below demonstrates what I mean.
Player in moving wall
I tried to use rigid body and collisions to help give me a solution, but that didn't stop the problem. I'm now not really sure what the best thing is to do.

Rigidbody should be able to do the trick. You said that it did not work, so here are a few things you need to make sure you have done for the Rigidbody collisions to work properly:
Give the player a Rigidbody component
Give the player a collider (best use capsule collider)
Give the wall a collider (it looks like a box collider would work best)
When you move the player, move them with the function Rigidbody.MovePosition(newPos) or by setting the velocity with Rigidbody.velocity = new Vector3(newVelocity)
The "Is Kinematic" checkbox of the player's Rigidbody component is un-checked (set to false)

Unity: Enemy objects passing through box collider on edges of background

I'm developing a simple 2D Unity game (which I'm very new to so sorry if this is a silly question!) in which my player can eat its enemies by colliding with them. This works fine as I'm just selecting the "is trigger" component for the enemies and using this code in my Player class:
private void OnTriggerEnter2D(Collider2D other)
{
Debug.Log("Hit detected");
Destroy(other.gameObject);
transform.localScale += new Vector3(x, y, z);
}
However, this means the colliders placed around the border of my background image aren't stopping the enemies. What's the best fix for this?

I don't understand very well your question. However it seems that your collisions are not working. So, remember that for have collisions actually taking place in your game you need to use colliders and that one of the two elements participating in the collision need to have the rigidbody component.
That will make the physics work in the engine, which triggers dont.
To check if that works you can debug with:
// called on collision
void OnCollisionEnter2D(Collision2D col)
{
Debug.Log("OnCollisionEnter2D");
}

From what I understood, you want only to detect triggers between the player and the enemies, but you still want these to collide with physic objects in your scene, such as background colliders.
One possible way to achieve this is to create a child object for the player object with a collider component with the trigger option set, and attaching a script to it to handle the triggers. Then, with the use of layers to group your player and enemy objects, you can uncheck the collision between them following: Edit -> Project Settings -> Physics 2D: "Layer Collision Matrix".

You can assign a script to any enemy, checking the distance with the player in each frame. Then you can Uncheck "is trigger"
Vector2.Distance

Colliders not working in Unity3D 2D Project

I have 2 colliders, its a game where I have a ball, and a Labyritnh. The ball should pass through the labyrinth and collides with the labyrinth's walls.
But I have a problem, the physic aren't working that well, the collider don't work.
I have a rigidbody and a collider in both of these objects.
Also, I have a problem with choosing box or edge colliders.
Because it is a labyrinth, I need to design the colliders with some complex shapes.
I have used edges colliders and box colliders but the ball is passing through all these colliders like nothing, It seems like its not working.
Can someone help me?

you need a rigid body object attached to at least one of them for the colloders to work.
make each wall individually and use rectangel colliders. add a rigidbody component, and set that rigid body to kinematic. should work then.

Collision between Box Collider 2D and Polygon Collider 2D not working

Currently I am working on a networked 2d platform game.
My player is an empty object which serves as a parent to my actual graphics etc. The empty object has a rigidbody (3d) attached to it as it needs to have one in order to use the configurable joint component ( note: I move my player around using this 3d rigid body).The player body however, a child to the graphics, has a box collider 2d attached to it as it after all it is a 2d game and has to collide with other 2d objects.
My platforms have polygon collider 2ds attached to them (which is connected to a platform effector if that is worth mentioning).
Now, even though both my player body (which is a child to graphics which is a child to my player object) and my platforms have 2d colliders on them they do not collide and can simply go inside each other (neither of them is marked as isTrigger).
In order to solve this I thought I would add a rigidbody 2D to the player body and see if that would do anything. Now upon adding the rigidbody 2D collisions did work but as soon as I made the rigidbody 2D have all position and rotation constraints ticked or as soon as I made it kinematic or static it would cease to collide with my platforms. The problem is I need to have the rigidbody 2D be static or not be able to move as I am currently moving my player object using the rigidbody (3d) attached to it and do not want any additional movement of the player body upon colliding with objects.
I know this is quite a lot of information, so if you have any questions or would like further information just comment and I will be quick to respond. Thank you :-)!
Edit:
2d ray casts are also unable to hit the player body box collider 2D
Edit 2:
So to recap:
If either the player body or the platform has a rigidbody 2d that is not static (dynamic) and can move collisions work. However currently I only have a rigidbody 2D on my player body which has to be static though (as explained earlier) as well as a box collider 2d. My platform(s) on the other hand currently only has a polygon collider 2d as I do not see why it would need a rigidbody 2D.

A static collider won't detect the collision with another collider if it doesn't have a rigidbody, if it is static or if it has a kinematic rigidbody. At least one of your two objects needs to not be static and to have a rigidbody which is not kinematic to be correctly detected. So you do need to add a Rigidbody2D to your platform.
When you have a doubt about why a collider wouldn't collide with another one, always refer to this page of Unity's documentation which sums up which kind of collider will collide with another one.

Rigidbody2D can't collide with Rigidbody3D, here's a workaround though
http://answers.unity3d.com/questions/580769/can-rigidbody-2d-collide-with-3d-colliders.html

Dragger with collider on Unity 3D

I´m making a simple CAD application on Unity 3D using C# to configure closets. I'm trying to limit the movement of the shelves so you can move them only on the hole, so I have a dragger attached to every piece of the closet I want to move, but obviously they can cross with each other.
I thought I could use the collider system that Unity has to limit this movement but since I never worked with Unity before I´m kinda lost. This is my dragger so far:
mousePosition = new Vector3(Input.mousePosition.x, cubo_tmp.transform.position.y, distance);
objPosition = Camera.main.ScreenToWorldPoint(mousePosition);
objPosition.Set(objPosition.x, cubo_tmp.transform.position.y, cubo_tmp.transform.position.z);
I keep y and z components so it can move only in one direction.

Box Colliders are best for cuboid shaped objects.
In the editor, if you click GameObject > 3d Object > Cube, Unity will add a cube with a Box Collider to your scene:
If you want to add a Box Collider to a GameObject that doesn't have one, click Add Component in the Inspector panel and type in "Box Collider" to find it. It looks like this:
Note: If the IsTrigger box is checked, the Collider acts as a Trigger rather than a Collider.
A GameObject with a Collider will "collide" with any other GameObject that also has a Collider, with a small exception involving 2 Mesh Colliders that are both set to Convex.
EDIT: I think you are able to intersect the objects because you are modifying Transform.position directly in your code. This might override the collision behaviour.
Also Go to Edit > Project Settings > Physics and make sure your layer collision matrix allows collisions for the layers on which your objects are placed.