This will help you to integrate MailChoimp API 3.0 using CURL command. Not only this you also have the tag updated, created based on your requriement.
Tag Creation will help you to bifrucate the mulitple forms data inside one Audience.
Here you can also modify user "subscribed" or "unsubscribed" or "cleaned" or "pending" based on your requirement.
On additon to this have also added Vanilla JS form validation for basic fields.
Do not forget to change your API key and Audience ID. Currently have added dummy text.
Mailchimp API Key
$api_key = 'XXXXXXXXXX';
Mailchimp Audience ID.
$list_id = 'XXXXXXXXXX';