No it’s not possible.
Generating keys – Envato generates keys for you called purchase codes. You can use the Envato API to validate them and get full details about the associated purchase. I have a small guide for this here.
Purchase codes are private and you won’t be able to see them unless the buyer sends them to you. Many themes ask for the code after installation to verify the purchase and provide automatic updates.
Newsletters – Definitely not possible, as you will never be able to get a buyer’s email address unless they themselves provide it to you somehow (e.g. by contacting you for support). You could add a “subscribe to our newsletter” form in your item’s backend. I’ve done that before and it was highly effective.