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What are the general instructions to add a new fragment that uses a new screen and has its own layout?

I'm struggling to figure out how to create fragments that have their own layout files and take up the whole screen, as opposed to adding them to the activity's layout.
For instance, in my activity there is a button which should call a RecyclerView Fragment that takes up the whole screen, let the user pick an item, and then return to the activity. All the examples I'm finding though use transactions to add or replace on the activity's layout. How do I make fragments that are inflated from their own layout files and call them from the activity?
And sorry, I'm sure there's a better way to ask but I'm just going through docs and vids trying to learn.

A few line difference between Fragment and Activity:
An Activity is an application component that provides a screen, with which users can interact in order to do something. More details: http://developer.android.com/guide/components/activities.html
Whereas a Fragment represents a behavior or a portion of user interface in an Activity. http://developer.android.com/guide/components/fragments.html

Android: How to open a new full screen fragment from a fragment

I would like to open a new full screen view (layout) from a fragment without have to create a new activity.
I know how to do it creating a new activity but I read you better "always" use multiple fragments, not multiple activities for your full project so I am following that "rule"
You can check the images attached to explain the situation I would like to reproduce. As you can see, from a fragment with a listview, it open a new full screen view. Tapping the back button in the action back, you go back to the main with navigation, toolbar and the list.
I am using xamarin but a suggestion using java will work too for me. I just need to understand the concept of how to do this and what kind of controls do they used.
Thanks in advance.

Adding views in layout from the app in Android

I want to develop an Android app, where start page of the app GUI, will contain 4 vertical layouts in the main layout. Now, in each layout, I want to add buttons/slider dynamically from the app (instead of adding buttons/slider dynamically in the source code). That means, initially all these 4 layouts will be blank and when user will select any button or slider in another layout, to add it in any of this 4 layouts, the button or slider will be added in that layout. User will be able to add max 10 views in any vertical layout and the views can be either button, slider or custom view.
My attempt:
First I tried to create 4 vertical layout under the main layout for startup page and I got succeed.
I also find after searching that its possible to add views dynamically in layouts in android.
dynamically adding a view to activity layout
But most examples, add views dynamically in android by running loops, instantiating the desired view class and then add it in the main layout. Although, in this way, views are added dynamically in the layout, it is done by modifying the source code.
Is it possible to write the source code in a way, so that it can be done directly from the app? So that when user will click on Add a slider in "layout 1", a slider will be added in layout 1 and then again, when the user will click on "Add a button" in layout 1, a button will be added at the end of the slider. User will be able to customize button or slider properties. Also, if the user change the value of the slider, the app will remember its value.
Now, next time, when the app will be opened, those views will be there in the layouts, they will not be deleted and the values will remain unchanged (for example, a ticked check box will remain ticked), so I think I also need some kind of storage or properties manager.
My question is, is it possible to do this in android (because I never seen such apps in android) and if possible, any idea, how can I implement it?
I am totally new to android, so my knowledge is limited but I completed the basic tutorials on android app development and I have plugin development experience in eclipse.
Thanks a lot in. I will highly appreciate your help.

Of course it is possible:
Every layout (like LinearLayout, RelativeLayout etc.) extends the ViewGroup-class, which offers the addView-method.
To add a new view (like a Slider) to one of your layouts, just instantiate it programmatically (via new) in your activity and assign the appropriate LayoutParams to it
To store the state of user added content, it is the easiest to use SharedPreferences - a simple key-value-store which holds data over the application's lifecycle

Yes. This is possible. To create the Views dynamically, you simply have to either extend the class of the View or just say new Button(Context, AttributeSet); (Not only for Button's every View has a constructor that takes an attribute set and a context).
Using Layout.addView() you can add any View to the Layout.
Using SharedPreferences you can indicate what View belongs in what Layout.
If you decide to extend the View's class, make sure not to do too much in it. I tried that once and it just gave me an OOM (OutOfMemory Error) because I had a ton a Views trying to do stuff at the same time.

java android view structure

Just a simple maybe stupid question.
Is it ok to use multiple activities at once in an android application using an Inflater? I want to have multiple views on my screen without losing the previous view. For example, a user clicks on a button and a information screen shows up. Start Intent would convert the whole screen to the information screen activity.
Using an Inflater works but I'm just wondering if its the right way to display multiple views. Thanks in advance.

You should be using Fragments for this. Each fragment has a view/layout and you can move them in & out of your main view as you require. There are many tutorials

You can set the visibility of the views, e.g.:
Button b = (Button)findViewById(R.id.button);
b.setVisibility(View.GONE);

How do you make custom widgets?

When using developing Widgets for Android it seems you are not able to add your own custom View classes to a AppWidgetProvider.
For example I created a custom class which extends View, this works fine when used within an Activity but the moment I add it to a Widget I get a "ClassNotFoundException" because Android seems to only allow a set of certain system widgets to be added.
I have seen some apps which look like they have made there own custom widgets. For example there is one that brings up a radial menu when clicked which shows application shortcuts. How are these being implemented? Is there a work around to using my own custom widget? They seem to have a canvas which they are able to draw on within the widget.
Okay quick example https://market.android.com/details?id=zombiesinthelab.widgets.droidpetwidget&feature=top-paid
So this widget is being done by just drawing ImageViews and updating them periodically opposed to using a canvas to draw the frames?

Android Widgets can only contain Layout-Widgets supported by RemoteViews. See this list:
A RemoteViews object (and,
consequently, an App Widget) can
support the following layout classes:
FrameLayout
LinearLayout
RelativeLayout
And the following widget classes:
AnalogClock
Button
Chronometer
ImageButton
ImageView
ProgressBar
TextView
> Descendants of these classes are not
supported.
Pay attention to the last sentence. You can not change this behaviour, it is hard coded in android.

I have not much idea on how to create widgets but following links can definitely help you:
1) http://developer.android.com/guide/topics/appwidgets/index.html
2) http://developer.android.com/guide/practices/ui_guidelines/widget_design.html