Hi @IBN
As issues related to Microsoft 365 Admin Center are not supported on Q&A forum currently, and the tag "office-itpro" focuses more on general issues of Office clients, so I would provide some information from Office's perspective.
> i would like to know more about the update release
According to the rolling out time of this update, and the link "Current Channel" at the bottom, for more details you can click this link.
Then you would find the Version 2204: April 26 (Build 15128.20178) that includes 2 parts: Feature updates and Resolved issues.
> To want know what channel we are currently on?
To check what channel you are on, you can go to one computer with Microsoft 365 Apps installed > Open one Office app > Account > Product Information, check the update channel.

> How can you test it?
If Microsoft 365 apps on users' machines do not install this update, then it's recommended to pick out some test machines to install this update to have a test.
- You can select the update channel with a late reception time for one group, such as Monthly Enterprise Channel and Semi-Annual Enterprise Channel. The another test one can set Current Channel, and check if there is any issue after the update.
To change the update channel, please refer to "Change the Microsoft 365 Apps update channel for devices in your organization". - You can also restrict specific update source for one group that get updates from Internet shared folder, the test group uses CDN by default to get Office updates automatically. If there is no issue after installing this update, you can download the update installation package to the update source and let other users update automatically.
For more details, you can checkout "Configure update settings for Microsoft 365 Apps" and "Choose how to manage updates to Microsoft 365 Apps".
> How will it impact our organization before testing it?
- If the Office update source is the default CDN, and automatic updates are also enabled by default, Office will automatically install the update without your testing.
- You can temporarily turn off Office automatic updates, after testing, then judge whether you need to upgrade to this version for users.
- Or you can change the update channel or specifcy the update source for certain users for a test.
> Also we would like to know if we choose targeted set of users for testing as per the option in O365 org settings, does this become applicable only to semi annual channel or monthly channel or current channel?
As the link said, selecting the appropriate update channel and using interval between update channels to test is a method.
In addition, as I reply above, you can also change update source for Office. But this requires more control costs.
For more information about Microsoft 365 updates, here is an article "Overview of update channels for Microsoft 365 Apps" you can have a look.
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