Storing plugin version number on activation and deleting it during plugin deactivation.

gistfile1.php

<?php

/**
 * Manging of version numbers when plugin is activated
 */
function MYPLUGIN_install() {

    // Add Upgraded From Option
    $current_version = get_option( MYPLUGIN_NAMESPACE . '_version' );
    if ( $current_version ) {
        update_option( MYPLUGIN_NAMESPACE . '_version_upgraded_from', $current_version );
    }

    update_option( MYPLUGIN_NAMESPACE . '_version', MYPLUGIN_VERSION );

    // Bail if activating from network, or bulk
    if ( is_network_admin() || isset( $_GET['activate-multi'] ) ) {
        return;
    }

    // Add the transient to redirect
    set_transient( '_' . MYPLUGIN_NAMESPACE . '_activation_redirect', true, 30 );
}
register_activation_hook( MYPLUGIN_PLUGIN_FILE, 'MYPLUGIN_install' );


/**
 * Manging of version numbers when plugin is activated
 */
function MYPLUGIN_deactivate() {

    delete_option( MYPLUGIN_NAMESPACE . '_version', MYPLUGIN_VERSION );

}
register_deactivation_hook( MYPLUGIN_PLUGIN_FILE, 'MYPLUGIN_deactivate' );