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Unity - How to rotate game screen?(Not mobile phone rotation)

I'm using Unity 2020.1.17f.
To do align correction between VR lens and Display, I want to control size of screen, offset of screen, and rotation of screen(screen means area of display where actual game scene is appeared, my game has letter box in 4 ways).
I could control size and offset by changing values of Viewport Rect, but I cannot find a way to control rotation of screen. (Like Cv2.GetRotationMatrix2D() of openCV in C#)
You can say "why don't you rotate your camera?", but rotating camera is not what I want. As you know, in VR, Game screen is distorted in several shapes to optimize to their lens shape. Thus, even I rotate camera, it is not helpful for mis-align correction.
In Google, there are many answers, but only related with rotation of mobile phone, not controlling rotation in arbitrary angle(that what i really want).
How can control of rotation of game screen?

You need to go to Edit/PlayerSettings/Player
And open the section called resolution and presentation
as you see there is a section called default orientation and here you can set the orientation of the build just opened.
Down there is also a section called Allowed orientations for auto rotations where you can set the other rotations allowed. In my case, everything is allowed, but you can just set the 2 landscapes or the 2 portraits depending on your game and your canvas and camera orientation

Unity 2D drag and drop without using Canvas

I have a board that made with bunch of square tiles, i have player which is circle and i wanna drop over the tiles and set plater postion to the center of nearest tile while mouse button up ;
is there any way to handle this without Canvas and EventSystem ?

There are a few ways to do it,
You can store all the tiles in an array and when dragging the player check for the position of the closest one, this can work great if you have gaps between tiles and want the player to still snap on to the tile even if the player is not over it by having a threshold setup, it could get a bit costly though if you have thousands of tiles and you are iterating through them all.
Second and the easiest one is to just cast a Raycast from your player straight to the plane where your tiles are positioned, on hit just position the player in the middle of the tile. If you have more objects in the scene you can also tag the tiles with for example "Tile" and in the raycast check for the tag. The use of raycasts is documented here https://docs.unity3d.com/ScriptReference/Physics.Raycast.html

Unity2D hide everything that is outside shape defined by edgecollider

I have a 2D polygon that is defined by a edgeCollider. Is there a way to hide everything that is outside of the shape and show only what is inside?
I tried using skyboxes and lights. I thought about creating a mask(but i dont know how to create such a mask).
Is there a way to only show what is inside the shape defined by edge collider?

What about using the colliders trigger events?
Set this polygon as a trigger in the edgeCollider2D component in the inspector. Then you can use the collider OnEnterTrigger2D.
Your gameobjects are all disabled until this edgeCollider collides with in. Then disable the gameobject OnExitTrigger2D.
If you wanted to limit it to a certain number of object only. You would set a layer to only hide/show these object.
void OnTriggerEnter2D(Collider2D other) {
if(other.gameObject.layer == "hiddenObject"){
other.gameObject.enable = true;
}
}
Then the reverse on the OnTriggerExit2D.
I'm not sure the effect that you are aiming for. So another solution could be a postprocessing shader.
I can only give a high level description on this however.
You would take the final screen image texture, and the current position of the polygon and then add the pixels from the screen texture to the polygon texture and output this texture. (this shader has to exists already).
But you want the inverse of these.
https://docs.unity3d.com/Manual/shader-TransparentCutoutFamily.html
You're wanting to keep what's in the hole and get rid of what's outside of it?
You can download the built in shaders to edit them here
https://unity3d.com/get-unity/download/archive
Just find your version of unity and select builtin shaders from the drop down.
Edit: "SPOTLIGHT!", try this but with your custom shape
http://www.shaderslab.com/demo-49---spotlight.html

Trying to create game objects aligned in screen responsively UNITY

i am trying to create game objects in the screen aligned from the center, they are just characters ordered from the center to the sides, i am pretty bad explaining things so i will just attach an image

VR score text display

I am trying to make a VR game with google cardboard in unity. However we can not find a way to display score text right in front of the player. However when I add 2D text it is only on one side and therefore on one side of the eye and getting the position right for 2 texts is hard. If I use 3D text and set in front of the players position I think it will go into the wall if a player hits one. Is their any way to display a score on google cardboard / Unity VR.

You can either use native Unity Canvas UI or Googles hack to render OnGUI calls onto a texture.
I would definately recommend Canvas as that is the way Unity is working on their UI features, and it has much better layout capability.
To use canvas, Right click in the hierarchy and add UI->Text. You will automatically get a canvas. The important part is set the canvas to world-space (not screen space overlay). Then drag the canvas game object so it is a child of the Google Cardboard Main head object. Scale it down (like x:0.001,y:0.001,z=0.001) because by default it will be massive. To avoid going through walls position it about 0.5m in front of the camera - within any collider you may have.

there is another approach as well which you can place that canvas under camera make it world space, and then adjust it as you want, after that where ever you look at it will be seen easily ( as suggested by earlier user in answers) as you can see below in picture i placed canvas > Text > under camera which i used for oculus/ google camera