Hey Robert, welcome to the community.  

For the updating interests, check out the answer in this post:

Regarding your 2nd point, I’m not quite sure what you mean.  Which subscription would you want them to confirm? Being subscribed to your email list?  if so, I’d recommend enabling double opt-in if it’s not already.  That way, you’ll get full consent of them wanting your emails.  Check out this link for more information:

https://help.klaviyo.com/hc/en-us/articles/115005251108-Guide-to-the-Double-Opt-In-Process

Hi @RobertEC,

Building off or @Mailbox Manny’s comment regarding your second point, although, we do not encourage asking for opt-in consent through campaign emails as you should have that prior to emailing the customer as best practice, there are instances where you have their email address due to purchase but not opt-in.

To get consent for these types of users in your account, I’d recommend creating a separate signup form for these users and targeting that form to them on your website. You can do this by creating a segment with the logic of “What someone has done > placed order at least once over all time AND Is not in main mailing list AND What someone has done > clicked email at least once over all time.” We want to add the clicked condition so that we can ensure that this form is only targeting these active “non opted in” contacts that have been cookied by Klaviyo. 

Hope this helps!

Julie