Including field variables in custom URL following FORMMAIL submissions

I would like to create custom pages for redirect following submission of forms through formmail.

I have two questions.

First, how do I access the variables that the formmail uses to include on my custom URL? That is, if I don’t include a custom URL, formmail automatically redirects to a page that repeats the information provided in the form … I would like to use some of these fields in my custom page. How do I call these? (They are php variables sent in the POST, I’m figuring, but my coding skills aren’t that adept)

Second, can I include a field for the user to check that will allow the formmail to be sent to themselves as well as me, in case they would like to keep a copy? I know how to add the field, but what programming do I need to add to have it sent? Or is this actually a function of the cgi and cannot be included? If not, can I have the autoresponder forward the email to the sender somehow?

Thank you