Check you've completed all the steps here: https://eepurl.com/dyil61 Hope that was helpful!
Yes, absolutely! You need to activate the GDPR consent forms and then add a form to your site. I'd explain it to you but this guide does a really good job: https://mailchimp.com/help/collect-consent-with-gdpr-forms/ If you need any help do let me know!
You need to think about these auto-responders in terms of events. If you can put data up on MailChimp when an event takes place, you can manage auto-responders off of that data. Here is some additional information from their website. http://kb.mailchimp.com/article/how-do-i-create-an-autoresponder