By default, UNA contains versions verification feature. It allows to detect which module is compatible with your UNA version. In all UNA versions <= 12.1.1, you can see modules in studio for download even if they are not compatible with your UNA version and when you try to install you will see the notification about incompatible versions. From version 13.0.0 and upper, you already can not see incompatible modules in Studio and thus can not downloaded them for installation.
If you install modules manually from github you should check file install\config.php of the module. It contains this section:
'compatible_with' => array( '13.0.x' ),
About PHP and other server's configuration: since modules are installed on UNA, they can be installed only on the same server where UNA is located, thus servers' requirements for modules are the same as for the UNA.
If there are any other special requirements for the module, they should be indicated in description of the module.
The all Messenger versions ( as any other products ) are available in Download area of module (see my screenshorts). The latest version which is compatible with UNA 12 is Messenger 12.0.5.
I understand now, A BIG THANKS for the answer, I didn't see that button.
It was better that when you press the download button, all the versions can be seen directly. without having to open another intermediate page to see all the versions.
I suggest you to remove the intermediate page where only see the latest version is visible. When you click on the download button, a list of all available versions will open.
Or to open several previous versions in the intermediate page, at least three and the button for more should be right below them MORE INTUITVE.
Simpler things are more practical, my self I searched for days without seeing that button.
I apologize for the inconvenience, but I did not expect there to be so many DEPTH pages