Advanced Power of PHP

Login page on DataGrid? What script do you speak about?

The Cron Job feature is already exist in the script. To change settings or write your own procedure, following the instructions below: 1. Settings. Change settings according to your needs. To do this, go to General -> Site Settings -> Cron Jobs . On this page you may change settings of running Cron ...

You may add your own options and then customize wizards to handle these options.

It's a guest value, don't put attention on this.
Seems it's written here by a mistake.

Do you mean you see this on Paypal page?
Create a ticket in support and provide them access to your website.

You have to check mod_rewrite. Open a ticket in support.

It must save the selected state.
Open a ticket in support and provide access to your website.

What do you mean "restore"?
What version of wizard you work with?

Turn on debug mode and see the error description.
In include/settings.inc.php
define('SITE_MODE', 'development');

Try to use default values:
viewtopic.php?f=33&t=1934