How use get_plugin_updates() function?

Welcome.

The function returns an array of all possible updates. Means that you need to specify the plugin that you need to get its information.

Sample output of get_plugin_updates call on admin_init:

array(1) {
  ["fast-velocity-minify/fvm.php"]=>
  object(stdClass)#7844 (14) {
    ["Name"]=>
    string(20) "Fast Velocity Minify"
    ["PluginURI"]=>
    string(23) "http://fastvelocity.com"
    ["Version"]=>
    string(5) "2.7.7"
    ["Description"]=>
    string(192) "Improve your speed score on GTmetrix, Pingdom Tools and Google PageSpeed Insights by merging and minifying CSS and JavaScript files into groups, compressing HTML and other speed optimizations."
    ["Author"]=>
    string(12) "Raul Peixoto"
    ["AuthorURI"]=>
    string(23) "http://fastvelocity.com"
    ["TextDomain"]=>
    string(20) "fast-velocity-minify"
    ["DomainPath"]=>
    string(0) ""
    ["Network"]=>
    bool(false)
    ["RequiresWP"]=>
    string(0) ""
    ["RequiresPHP"]=>
    string(0) ""
    ["Title"]=>
    string(20) "Fast Velocity Minify"
    ["AuthorName"]=>
    string(12) "Raul Peixoto"
    ["update"]=>
    object(stdClass)#7799 (12) {
      ["id"]=>
      string(34) "w.org/plugins/fast-velocity-minify"
      ["slug"]=>
      string(20) "fast-velocity-minify"
      ["plugin"]=>
      string(28) "fast-velocity-minify/fvm.php"
      ["new_version"]=>
      string(5) "2.7.8"
      ["url"]=>
      string(51) "https://wordpress.org/plugins/fast-velocity-minify/"
      ["package"]=>
      string(69) "https://downloads.wordpress.org/plugin/fast-velocity-minify.2.7.8.zip"
      ["icons"]=>
      array(1) {
        ["1x"]=>
        string(73) "https://ps.w.org/fast-velocity-minify/assets/icon-128x128.jpg?rev=1440946"
      }
      ["banners"]=>
      array(1) {
        ["1x"]=>
        string(75) "https://ps.w.org/fast-velocity-minify/assets/banner-772x250.jpg?rev=1440936"
      }
      ["banners_rtl"]=>
      array(0) {
      }
      ["tested"]=>
      string(5) "5.3.2"
      ["requires_php"]=>
      string(3) "5.6"
      ["compatibility"]=>
      object(stdClass)#7800 (0) {
      }
    }
  }
}

So you need to specify the plugin before getting its name. You need to change the code to something like the following one:

$plugin_updates = get_plugin_updates();

// Print plugin name.
echo ['my-plugin/my-plugin.php']->Name;

// Print plugin update version.
echo ['my-plugin/my-plugin.php']->update->new_version;