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Outlook VSTO - Allow specific AD group to see ribbon

How can I programmatically restrict the VSTO Add-in Ribbon visibility to a specific AD group only? Can this be controlled directly from the Ribbon XML itself? The plugin is distributed to entire org, but need the ribbon visibility to change by AD group

No, but your own code can easily perform the check and show/hide the ribbon using the getVisible callback specified for your ribbon.
Would be a good idea to perform that check asynchronously and cache the check result before the ribbon is requested by Outlook. If the check completes after the ribbon is returned, call RibbonUI.Invalidate(), which would case Outlook to invoke your getVisible callback again.

Programmatically get the list of the ribbons using VSTO add-in

I have created a C# VSTO add-in with Visual Studio 2019 that receives commands from a socket connection and it can insert text, modify buttons only in my ribbon using office Interop.
I want to know two things.
How can I get the name of all the ribbons (Home, Insert, Design,
....) programmatically?
Initiate a mouse click (for example click Bold button in the Home tab) on any other ribbons than the one I created.
For the 2nd question, I want to use office add-in only, not by simulating keypress/mouse event.

How can I get the name of all the ribbons (Home, Insert, Design, ....) programmatically?
There is no trivial way for getting this job done. You can try using Accessibility API. Microsoft Active Accessibility is a Component Object Model (COM)-based technology that improves the way accessibility aids work with applications running on Microsoft Windows. It provides dynamic-link libraries that are incorporated into the operating system as well as a COM interface and API elements that provide reliable methods for exposing information about UI elements.
Initiate a mouse click (for example click Bold button in the Home tab) on any other ribbons than the one I created.
You can use the CommandBars.ExecuteMso method which executes the control identified by the idMso parameter. This method is useful in cases where there is no object model for a particular command. Works on controls that are built-in buttons, toggleButtons, and splitButtons. On failure, it returns E_InvalidArg for an invalid idMso, and E_Fail for controls that are not enabled or not visible.
Application.CommandBars.ExecuteMso("Copy")

Accessibility API (as Eugene mentioned) is pretty much the only way to drive Outlook Ribbon and its controls. Keep in mind that since Microsoft has never documented the controls and their ids, they are subject to change between the versions.
If using Redemption (I am its author) is an option, it exposes SafeExplorer and SafeInspector objects that expose the ribbon and its controls using Accessibility and low level Windows API.
Redemption.SafeExplorer sExplorer = new Redemption.SafeExplorer();
sExplorer.Item = OutlookApplication.ActiveExplorer;
foreach (var tab in sExplorer.Ribbon.Tabs)
{
MessageBox.Show(tab);
}

Add a button to Outlook message ribbon

I'm totally newbie in Office Add in Development.
Started few hours ago :)
Office version: 2016
I would like to create an add-in, with a button that will allow me to synchronize my email with my custom program and "flag" it to avoid a new synchronization in the future.
For that, it would be necessary to:
add a button (it seems simple to me, but by following this link, I did not manage to see the button when debugging in Outlook)
I would like the button is present in the ribbon that appears when you open an email, and only down (it would prevent a synchronization of several emails at once) - and I can not find the name of the adequate control. There is a list of Excel files (here) but which corresponds to the one of the opening of the mail message?
perform any action when the user clicks the button - I guess that's a simple event of the button, but how can I get the opened message data and metadata (sender, to, cc, subject ...)
"flag" the email, so as to avoid a second synchronization. The ideal is to add an icon to the email in the list of emails, as is done for an email containing attachments etc ...
I know I'm asking a lot, but I'm not asking to get the job done, just to be able to steer in the right direction. So if you have tutorials, articles etc ... to help me, it would be great.
Thank you
N.B.: Copy of this question has been posted in VSTO forum here

To create a custom ribbon UI, VSTO provides two possible ways:
Walkthrough: Create a custom tab by using the Ribbon Designer
Walkthrough: Create a custom tab by using Ribbon XML
To keep a separate state for the control for each inspector window separately you need to implement ribbon callbacks and call the Invalidate or InvalidateControl methods of the IRibbonUI interface. Read more about these methods in the following articles:
OfficeTalk: Display and Hide Tabs, Groups, and Controls on the Microsoft Office Ribbon User Interface (Part 1 of 2)
OfficeTalk: Display and Hide Tabs, Groups, and Controls on the Microsoft Office Ribbon User Interface (Part 2 of 2)
The Fluent UI (aka Ribbon UI) is described in depth:
Customizing the 2007 Office Fluent Ribbon for Developers (Part 1 of 3)
Customizing the 2007 Office Fluent Ribbon for Developers (Part 2 of 3)
Customizing the 2007 Office Fluent Ribbon for Developers (Part 3 of 3)

Accessing control inside a ribbon in Outlook using VSTO

i am trying to access a label in builtIn ribbon and trying to change its visibility inside a background worker. But its not working.
My Code is
Globals.Ribbons.MailReadItemRibbon.verifyLabel.Visible = true;
If anyone know what i am doing wrong. Please help.

First of all, you should't access any UI controls from secondary threads. It is allowed to make any changes to the UI on the main thread only. You may consider using the Control.Invoke method which executes a delegate on the thread that owns the control's underlying window handle.
Second, the Fluent UI (aka Ribbon UI) is a static thing from its birth. The only possible dynamism is callbacks. So, I'd recommend using callbacks with the IRibbonUI's Invalidate or InvalidateControl methods instead. Take a look at the following articles for the sample code:
Chapter 11: Creating Dynamic Ribbon Customizations (1 of 2)
Chapter 11: Creating Dynamic Ribbon Customizations (2 of 2)
For each of the callbacks the add-in implements, the responses are cached. For example, if an add-in writer implements the getImage callback procedure for a button, the function is called once, the image loads, and then if the image needs to be updated, the cached image is used instead of recalling the procedure. This process remains in-place until the add-in signals that the cached values are invalid by using the Invalidate method, at which time, the callback procedure is again called and the return response is cached.
The Fluent UI (aka Ribbon UI) is described in depth in the following series of articles:
Customizing the 2007 Office Fluent Ribbon for Developers (Part 1 of 3)
Customizing the 2007 Office Fluent Ribbon for Developers (Part 2 of 3)
Customizing the 2007 Office Fluent Ribbon for Developers (Part 3 of 3)

Get callback from custom tab in office backstage

I created a custom tab at the backstage view in Office 2010. Like this.
Now what i want to have is an event, that triggers when my tab is being pressed. Unfortunately the tab does not have an OnAction method or something like that.
Any ideas?

There is no such event for tabs. But you can specify getVisible callback for any control on that tab. Thus, the callback will be invoked at least when the tab is clicked for the first time.
You can read more about the Fluent UI (aka Ribbon UI) in the following series of articles in MSDN:
Customizing the 2007 Office Fluent Ribbon for Developers (Part 1 of 3)
Customizing the 2007 Office Fluent Ribbon for Developers (Part 2 of 3)
Customizing the 2007 Office Fluent Ribbon for Developers (Part 3 of 3)