The plugin requires WordPress 4.2 and PHP 5.3+ to be installed on your server.
Just download and install the plugin, upon activation, if your host is not running on PHP 5.2 the plugin will not activate and will display a message warning you that your host is running an extremely old version of PHP.
If your host is running PHP 5.2 or less, you are using a deprecated version of PHP not supported anymore by PHP itself, this also leaves you vulnerable to potential security issues.
WP User Manager is free and will always be free to use and download. Paid extensions are available and allow you to enhance the power of WPUM even more.
Yes, if you require support please send a request.
Yes, we provide an extensive online documentation here.