1) 3.2.2 is not a valid release number (its only the version of the Xampp Controlcenter). The version of Xampp is identical to the version of the included PHP, currently Xampp 7.1.3.3 and Xampp 7.2.24 and Xampp 7.3.11. See
https://www.apachefriends.org/de/download.html2) There is no upgrade instruction, you have to do a full backup (most important!), a full de-install and a full new install. Finally you have to restore your own applications, data and configurations. Its quite a task.
3) No, Xampp does not support upgrade of single components like Apache, PHP, MariaDB etc.
That is the disadvantage of using Xampp. Therefore Xampp comes preconfigured and is running out of the box.