Tried in different ways but sidebar not working?

add_action( 'widgets_init', 'Y_widget_register' );

You have a typo – use underscores.

Here is the working piece:

function Y_widget_register() {
register_sidebar(array(
    'name' => esc_html__('Sidebar', 'Y-07'),
    'id' => 'y-sidebar',
    'description' => 'Dynamic Right Sidebar',
    'before_widget' => '<section id="%1$s" class="y-widget %2$s">',
    'after_widget' => '</section>',
    'before_title' => '<h2 class="y-widget-title">',
    'after_title' => '</h2>'
));
}

add_action('widgets_init', 'Y_widget_register');