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Visual Studio Form Designer Showing List of Controls

I know that getting the Form Designer to work is a ticklish business. Generics, x64, subtle problems with the project's XML... But perhaps someone can offer advice about my current problem, which is that a component I created that inherits from TabPage, when I try to view it in the designer shows up as a list of its controls, like this:
Thanks in advance.

You cannot make a TabPage as root of the designer, while you can do the same for a Panel or other container controls. The limitation is because, TabPage can only be hosted in TabControl, not even in the overlay control of the designer:
TabPage cannot be added to a
'System.Windows.Forms.Design.DesignerFrame+OverlayControl'. TabPages
can only be added to TabControls.
A control can be shown as root of the designer when the base class of the control has designer of type of DocumentDesigner. Form and UserControl are such controls which means when you create a new Form1:Form or new UserControl1:UserControl, since the base class derived from a designable control, then the class can be edited in the designer as root.
I believe you can handle your requirement by using UserControl, but for learning purpose (or as a workaround) if you want to make a control deriving from Panel designable, you can copy the following code in a code file:
public class MyControl: MyDesignableControl
{
}
[Designer(typeof(DocumentDesigner), typeof(IRootDesigner))]
public class MyDesignableControl : Panel
{
}
Then save it and then double click on it and you can see you can design it like a root control.
Then after you done with the design, change the Panel to TabPage.
Remarks on
DocumentDesigner
This designer is a root designer, meaning that it provides the
root-level design mode view for the associated document when it is
viewed in design mode.
You can associate a designer with a type using a
DesignerAttribute.
For an overview of customizing design time behavior, see Extending
Design-Time
Support.

How to expose ALL properties of a Control in a class derived from Form?

I have class derived from Form and it contains a TableLayoutPanel and in it one Label and one Panel. When I create instance of this Form, all properties and events of controls in design editor are read-only. Is there any way how to expose whole object for editing? I know that I can expose properties one by one, but that is not the best way in case when you want all of them.

Have a look here:
Avoid Visual Inheritance
The TableLayoutPanel control does not support visual inheritance in
the Windows Forms Designer. A TableLayoutPanel control in a
derived class appears as locked at design time.

You can use internal or make a getter method / property
public Label GetLabel() => return someLabel;
or
public Label MyLabel { get { return someLabel; } }
or
internal Label someLabel;

How to Share Common Groups of Controls in Winforms C#

The majority of my forms for my project include an OK and Cancel button. (always positioned at the bottom right of the form). Currently I have a base class that inherits from System.Windows.Forms which contains an OK and Cancel button. All forms that use this then inherit from this base form class. Is there a better way of doing this that takes localization into consideration?

I would use MDI Child Forms for this. Parent Form Can contain OK/Cancel button where as you would have your child form in MDI container.
For More help visit
https://msdn.microsoft.com/en-us/library/aa984329(v=vs.71).aspx

You could just create a single form that has an empty panel or table layout, where you dynamically load the desired user control. It is basically the composition over inheritance principle.
public partial class MyFormWithButtons : Form
{
public MyFormWithButtons(UserControl control)
{
InitializeComponent();
control.Dock = DockStyle.Fill;
myPanel.Controls.Add(control);
}
}

Doing form inheritance is very useful in many levels:
Make a base form, and name it for ex: FrmBase.
Add the Ok, Cancel Buttons to it and set the Anchor property for both to Bottom.
Set the Buttons "Modifiers" property to "Internal", this way you can access these buttons from inherited forms:
Make as many forms as you want and make each inherit from the FrmBase ex: Form1 : FrmBase
now you can access the buttons from this from, using the properties.
Hope this being useful for you.

Is there a way in C# to create a design template for a component

Is there a way in C# to create a design template for a component (a button for example) All the buttons in the project will inherit the design from the template.
And whenever I change the template all the buttons will inherit the change.
I want that my application will have the same look
all the buttons will look the same, all the text box.....
Thanks

what you want to do can be achieved by creating your own inherited class of a control. e.g.
public class yourbuttontemplate : System.Windows.Forms.Button
{
yourbuttontemplate() //constructor
{
this.Height=20;
this.Width=40;
this.BackColor=Color.Blue;
}
}
Once you build your project, your button should be available in the toolbox and you can use this button instead of the default Windows.Forms.Button.

Show an instance of a component class in main form in c#

If I add a component class to my project containing some common controls, how can I display an instance of it in a panel in my main form?
I use this to create an instance of my class:
Component test = new Component1();
where Component1 is the name of my Component class
Then how could I do something like:
panel1.Controls.Add(test); ?
Or is there a way to do this without using Panels?

You are using the wrong class. A Component cannot be a child of a panel or a form, it doesn't have a visual presentation. The missing Handle property is the important one.
You need a Control. Derive your class directly from Control or from one of the built-in control classes (Button, Label, etc). You'd do the latter if you want to customize their behavior and make it re-usable.

Then how could I do something like: panel1.Controls.Add(test); ?
This is the correct way.
Or is there a way to do this without using Panels?
You could add your control to something other than a panel; for instance, to the form itself: Controls.Add(test).